July 1, 2009 · 2:00 AM

Does Weight Loss Prevent Type 2 Diabetes?

Finger-pricking four times a day gets old real quick!

Finger-pricking four times a day gets old real quick!

I found an interesting statistic in a scientific journal article last year:

Every 2.2 pound (1 kg) loss of excess weight lowers the risk of developing type 2 diabetes by 16%.

That tidbit was embedded in another article with a focus on regain of lost weight over time.  The “16% per kilogram” number sounded too good to be true, and I had never heard it before.  So I did some digging and found the source of the statistic.  Ain’t the Internet wunnerful?

The origin of the 16% figure is the Diabetes Prevention Program Research Group.  Investigators enrolled 1,079 middle-aged (mean 50.6 years) study participants and followed them over 3 years, noting the effects of exercise, percentage of fat in the diet, and weight loss on the subsequent development of diabetes.  Average body mass index was 33.9.  (A 5-foor, 4-inch person weighing 197 pounds (89.5 kg) has a BMI of 33.9).  Sixty-eight percent of participants were women.  The investigators’ goal for this group of overweight people was for loss of 7% of body weight through diet, physical activity, and periodic counseling sessions.  Average weight loss over the course of three years was 9 pounds (4.1 kg).

None of the study participants had diabetes at the time of enrollment.  But, by design, they all had laboratory-proven “impaired glucose tolerance.”  Impaired glucose tolerance is a form of “pre-diabetes.”  It is determined by giving a  75-gram dose of glucose by mouth, then measuring blood glucose (sugar) 2 hours later.  A blood glucose level under 140 is normal.  If the level is 140-199, you have impaired glucose tolerance.

Having impaired glucose tolerance means that study participants’ glucose (sugar) metabolism was already abnormal.  They were at higher than average risk of developing diabetes, compared with both average-weight healthy people and overweight people without impaired glucose tolerance.  This is a great cohort to study for development of diabetes.  But the finding that “every 2.2 pounds of weight loss lowers the risk of diabetes by 16%” applies to this particular group with impaired glucose tolerance, not the general overweight population.

A total of 153 participants developed diabetes over the course of 3 years.  Loss of excess weight was by far the best predictor of lowered diabetes risk, compared with regular exercise and lowering percentage of dietary fat.

Yes, weight loss does prevent diabetes in some, probably many, overweight people.  The specific degree of reduced risk depends on numerous factors, such as age, sex, genetics, degree of weight loss, and pre-existing impaired glucose tolerance.

Steve Parker, M.D.

Reference: Hamman, Richard, et al.  Effect of Weight Loss With Lifestyle Intervention on Risk of Diabetes.  Diabetes Care, 29, (2006): 2,102-2,107.

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June 30, 2009 · 2:00 AM

Are High-Protein Weight-Loss Diets Safe and Effective?

Animal protein

Animal protein

According to researchers at Tufts University, high-protein weight-loss diets may be effective and safe except for people prone to kidney stones, chronic kidney disease, and people with diabetes.  Long-term effects on bone health – osteoporosis, specifically – might be a problem.

High-protein weight-loss diets have been popular for a while.  “Protein Power” by Drs. Michael and Mary Eades is an example.  The Atkins diet may be, too.  If you increase the protein in your diet, you generally are decreasing carbohydrates or fat, or both, at the same time.   

I found a scientific review article from way back in 2002 and thought I’d share some of the highlights.  The authors seem very thorough; the article has 150 citations of other research articles. 

Note that the RDA – recommended dietary allowance – for protein is 0.8 gm/kg.  The typical U.S. resident eats about 1.2 gm/kg of protein daily, which is about 15% of total energy (calorie) intake.   Public health agencies recommend that we get 15% of our energy from protein, 30% from fat, and 55% from carbohydrate.  The authors of the study at hand propose that a high-protein diet be defined as:

  • protein intake of at least 25% of energy in weight-stable individuals, or
  • at least 1.6 gm/kg (of ideal body weight)  in people actively losing weight

Here are some of the authors’ points I found interesting:

  1. Higher-protein meals do seem to suppress hunger and enhance satiety, so high-protein dieters probably eat less (average 9% less calories).  It’s unknown if the effect lasts longer than six months.  Most of the evidences is much shorter-term.
  2. High-protein intake increases the thermic effect of feeding, meaning energy expenditure increases simply as a result of eating protein.  In other words, it takes energy to process the food we eat.  Compared with fats and carbohydrates, protein contributes twice as much to the thermic effect of feeding.  Most of the thermic effect of protein results from protein synthesis, i.e., the production of new proteins, which requires energy.  This has a minimal influence on body weight. 
  3. The authors write that “these studies do not support a role for high dietary protein in preventing loss of lean tissue during negative energy balance [actively cutting calories to lose weight], provided that dietary protein intake at least meets the RDA.”   
  4. They found only one study comparing a high-protein diet (25% of calories) with a low-fat, high-carbohydrate diet (12% protein).  Both diets were 30% fat.  Both groups could eat all they wanted.  Weight and fat loss were greater in the high-protein group, about twice as much. 
  5. High-protein diets over the long run may cause low-grade metabolic acidosis, leading to net loss of body calcium through the urine, with associated weak bones and kidney stones.   Animal proteins in particular do this.  Bone loss may be alleviated by calcium supplementation.  Fruits and vegetables may counteract the acidosis effect.  Nearly all of these statements are based on short-term studies.
  6. People with chronic kidney disease (ask your doctor) have slower disease progression and live longer if they limit protein to the RDA level. 
  7. Animal protein intake is directly related to risk of symptomatic kidney stones.
  8. Protein produces a blood glucose response, although not as much as with carbohydrate.  Insulin response is also seen.  In type 2 diabetics, the insulin response to 50 grams of animal protein was the same as to 50 grams of glucose.  A few studies suggest that in type 2 diabetics a high-protein diet may be detrimental to glucose control and/or insulin sensitivity.  Also note that people with diabetes are prone to chronic kidney disease, which could be worsened with a high-protein diet.  

Take-Home Points

See first paragraph.  The article authors may have different opinions now, based research published over the last seven years. 

Steve Parker, M.D.

Reference:  Eisenstein, Julie, et al.  High-protein weight-loss diets:  Are they safe and do they work?  A revew of the experimental and epidemiologic data.  Nutrition Reviews, 60 (2002): 189-200.

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June 29, 2009 · 2:00 AM

Mediterranean Diet Reduces Risk of Type 2 Diabetes

The traditional Mediterranean diet has long been associated with lower risk of developing cardiovascular disease, cancer, and dementia.  The diet is rich in olive oil, fruits, nuts, cereals, vegetables, and fish but relatively low in dairy products and meat.  Several recent studies suggest the Mediterranean diet may also help prevent type 2 diabetes.

Researchers at the University of Navarra in Spain followed 13,380 non-diabetic university graduates, many of them health professionals, over the course of 4.4 years.  Average age was 38.  I assume most of the study participants lived in Spain, if not elsewhere in Europe (the article doesn’t say).  Dietary habits were assessed at the start of the study with a food frequency questionnaire.  Food intake for each participant was scored by adherence to the traditional Mediterranean diet.  Participants were labelled as either low, moderate, or high in adherence.  Over an average follow-up of 4.4 years, 33 of the study participants developed type 2 diabetes.  Compared to the participants who scored low on adherence to the Mediterranean diet, those in the high adherence category had an 83% lower risk of developing diabetes.  The moderate adherence group also had diminished risk, 59% less.

How could the Mediterranean diet protect against diabetes?  The authors note several potential mechanisms: high intake of fiber, low amounts of trans fats, moderate alcohol intake, high vegetable fat  intake, and high intake of monounsaturated fats relative to saturated fats.  Olive oil, loaded with monounsaturated fats, is the predominant fat in the Mediterranean diet.  In summary from the authors:

Diets rich in monounsaturated fatty acids improve lipid profiles and glycaemic control in people with diabetes, suggesting that a high intake improves insulin sensitivity.  Together these associations suggest the hypothesis that following an overall pattern of Mediterranean diet can protect against diabetes.  In addition to having a long tradition of use without evidence of harm, a Mediterranean diet is highly palatable, and people are likely to comply with it.

Please give serious consideration to the Mediterranean diet, especially if you are at risk for developing type 2 diabetes.  Major risk factors include sedentary lifestyle, overweight, and family history of diabetes.

Steve Parker, M.D.

Reference: Martinez-Gonzalez, M.A., et al.  Adherence to Mediterranean diet and risk of developing diabetes: prospective cohort study.  British Medical Journal, BMJ,doi:10.1136/bmj.39561.501007.BE (published online May 29, 2008).

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June 25, 2009 · 9:57 AM

Which Components of the Mediterranean Diet Prolong Life?

We're pro-life

We're pro-life

Researchers at Harvard and the University of Athens (Greece) report that the following specific components of the Mediterranean diet are associated with lower rates of death:

  • moderate ethanol (alcohol) consumption
  • low meat and meat product intake
  • high vegetable consumption
  • high fruit and nut consumption
  • high ratio of monounsaturated fat to saturated fat
  • high legume intake

Minimal, if any, contribution to mortality was noted with high cereal, low dairy, or high fish and seafood consumption. 

The researchers examined diet and mortality data from over 23,000 adult participants in the Greek portion of the European Prospective Investigation into Cancer and nutrition.  You’ll be hearing more about the EPIC study for many years.  Over an average follow-up of 8.5 years, 1,075 of participants died.  652 of these deaths were of participants in the lower half of Mediterranean diet adherence; 423 were in the upper half.

Alcohol intake in Greece is usually in the form of wine at mealtimes. 

The beneficial “high ratio of monounsaturated fat to saturated fat” stems from high consumption of olive oil and low intake of meat. 

It’s not clear if these findings apply to other nationalities or ethnic groups.  Other research papers have documented the health benefits of the Mediterranean diet in at least eight other countries over three continents. 

The researchers don’t reveal in this report the specific causes of death.  I expect those data, along with numbers on diabetes, stroke, and dementia, to be published in future articles, if not published already.  Prior Mediterranean diet studies indicate lower death rates from cardiovascular disease and cancer.   

Steve Parker, M.D.

Reference:  Trichopoulou, Antonia, et al.  Anatomy of health effects of the Mediterranean diet: Greek EPIC prospective cohort study.  British Medical Journal, 338 (2009): b2337.  DOI: 10.1136/bmj.b2337.

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June 25, 2009 · 2:00 AM

Mediterranean Diet Cuts Risk of Diabetes After Heart Attack

In a blog post last year I discussed how the Mediterranean diet reduces the incidence of type 2 diabetes in healthy people.  I found another scientific journal article that examined the effect of various lifestyle factors that might influence the onset of type 2 diabetes in a different population: people who have had a recent heart attack.

Dariush Mozaffarian and colleauges studied 8291 Italians who had suffered a heart attack within the previous three months, but who did not have diabetes at the time of the heart attack.  Each study participant was followed for an average of 3.2 years to see if diabetes developed.  The researchers devised a Mediterranean diet score (range 0-15) incorporating consumption of cooked and raw vegetables, fruit, fish  and olive oil.  They also looked at consumption of butter, oils other than olive oil, cheese, wine, and coffee.  Participants’ dietary habits were assessed and scored three times over 1.5 years.  A number of other demographic, clinical, and lifestyle risk-factors were assessed.

The study did not survey other components of the Mediterranean diet, such as legumes, nuts, and grains.  This is a weakness of the study.  I suspect it relates to the fact they were using information from the GISSI-Prevenzione study, which was designed to evaluate fish oil and vitamin E in people who had had a heart attack, and researchers did not want to burden outpatient cardiology offices with full-scale questionnaires.

Over the three years of the study, 12% of participants developed new-onset diabetes, or 3.7% per year.  If not for the recent heart attack, the expected incidence rate for development of diabetes would be roughly 1.2% per year.  An even larger percentage, over 25%, of participants developed impaired fasting glucose, a kind of prediabetes that often develops into full-blown diabetes over time.

Was there anything about the people who developed diabetes that distinguished them from those who did not?  Yes – they tended to have older age, higher body mass index, high blood pressure, and they smoked.  Current smoking was associated with a 60% higher risk.  Every unit of higher body mass index, e.g, going from BMI 26 to 27, increased the risk by 9%.  High blood pressure increased the risk by 22%.

What about Mediterranean diet score?  The higher Mediterranean diet scores – score of 11-15 compared to 0-5 – were associated with 35% lower risk of diabetes.  A reduction in onset of impaired fasting glucose was similar.

The authors cite another study of 2499 patients with stable angina pectoris or remote heart attack (over 6 months perviously).  Twenty-two percent of them (one in five) developed diabetes or impaired fasting glucose over six years of follow-up, a rate of 4.1% per year.

The researchers write:

The lower risk associated with a Mediterranean-type diet suggests that diet could help reduce incidence of prediabetes and diabetes after a myodcardial infarction.  Many, though not all, trials have indicated that a Mediterranean-type diet lowers risk factors linked to insulin resistance and diabetes, including serum triglycerides, HDL cholesterol, systemic inflammation, endothelial function, and insulin sensitivity.  These physiological effects in short-term randomized trials provide biological plausibility for the inverse association between consumption of a Mediterranean-type diet and incidence of [impaired fasting glucose] and diabetes in this study.

What are the take-home points of this study for people – Italians, at least – who have had a recent heart attack?

  1. A recent heart attack is a risk factor for development of diabetes and prediabetes.
  2. The risk of developing diabetes and prediabetes may be significantly reduced by smoking cessation, prevention of weight gain, and consumption of typical Mediterranean foods.

Patients with both heart attacks and diabetes  have significantly worse outcomes  than people with only one of these conditions.  Since we can prevent many cases heart attack and diabetes through diet modification, why not?

Steve Parker, M.D.

Reference:  Mozaffarian, Dariush, et al.  Incidence of new-onset diabetes and impaired fasting glucose in patients with recent myocardial infarction and the effect of clinical and lifestyle risk factors.  Lancet, 370 (2007) 667-675.

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June 24, 2009 · 2:00 AM

High Protein Ketogenic Diet Beats High Protein/Medium Carb Diet in Men, at Least Short-Term

Low-Carb Steak

Low-Carb Steak

Scottish researchers last year reported greater weight loss and less hunger in obese men on a high-protein ketogenic diet compared to a high-protein, moderate-carbohydrate diet.

Background

Dietary protein seems to be more satiating – able to satisfy hunger, that is – than carbohydrate and fat. 

The typical Western (especially American) diet derives about 55-60% of total calories from carbohydrates.  When carbohydrate intake is very low, under 20-30 grams per day for example, fat stores are utilized as a source of energy to replace carb calories, resulting in fat breakdown waste products called ketone bodies.  These are ketogenic diets.  In them, carbs are replaced usually by both extra fat and extra protein. 

Methodology

Each of 17 obese men, 20 to 65 years old, were placed on two separate diets for four weeks each time.  Average weight was 111 kg.  Average body mass index was 35.  This was a residential program, but the subjects were allowed to leave and go to work.

  • Diet 1:  high-protein, low-carbohydrate, ketogenic.  30%, 4%, and 66% of energy (calories) as protein, carbohydrate, and fat, respectively.
  • Diet 2:  high-protein, medium-carbohydrate, nonketogenic.  30%, 35%, and 35% of calories as protein, carb, and fat, respectively.

Actually 20 men signed up, but three dropped out for personal reasons after starting. 

They could eat as much as they wanted. 

Results

Subjects had no overall preference for either diet.  No differences in the diets for desire to eat, preoccupation with food, or fullness.  Weight loss was greater for the low-carb diet tahn with the medium-carb diet: 6.34 kg vs 4.35 (P < 0.001).  Subjects lost more weight on their first diet than on their second.  Fasting glucose and HOMA-IR (a test of insulin resistance) was lower than baseline for the low-carb diet but not the other.  Total and LDL cholesterol were tended to fall in response to both diets, but to a statistically significantly great degree only on the medium-carb diet.  When eating the low-carb diet, subjects ate 300 calories per day less than on the medium-carb diet.  [ketones were measures?]

Discussion

We have to assume that study subjects were of Scottish descent.  Applicability of these results to other ethnic groups is not assured.  Similarly, results don’t necessarily apply to women.

I’m surprised the medium-carb dieters, eating all they wanted, lost weight at all.  Must be a result of the high protein content or lower-than usual carbohydrate content of the study diet.  Study authors cite others who found that doubling protein intake from 15 to 30% of calories reduces food intake, which should lead to weight loss. 

Since protein content was the same on both diets, the greater weight loss seen on the low-carb ketogenic diet was the result of lower caloric intake, in turn due to less hunger.  The reduced energy intake could be due to lower carb or higher fat intake, or both.  The researchers cite one study finding no satiating effect of fat.  Some say that ketone bodies reduce appetite. 

Although the medium-carb diet showed greater improvements in total and LDL cholesterol, the low-carb diet changes trended in the “right” direction (down).

On the low-carb ketogenic diet, lower glucose levels and insulin resistance would tend to help people with (or prone to) type 2 diabetes, prediabetes, and some cases of metabolic syndrome. 

Steve Parker, M.D.

 References: 

Johnstone, Alexandra, et al.  Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum.  American Journal of Clinical Nutrition, 87 (2008): 44-55.

Weigle, D.S., et al.  A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations.  American Journal of Clinical Nutrition, 82 (2005): 41-48.

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June 23, 2009 · 2:00 AM

Comparison of Mediterranean, Low-Carb, and Low-Fat Weight-Loss Diets

The July 17, 2008, issue of the New England Journal of Medicine has a well-done study comparing the Mediterranean, low-carb, and low-fat weight-loss diets in an Israeli population over the course of two years.  The researchers conclude that “Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets.  The more favorable effects on lipids (with the low-carbohydrate diet) and on glycemic control (with the Mediterranean diet) suggest that personal preferences and metabolic considerations might inform individualized tailoring of dietary interventions.”

How was the study set up?

Moderately obese participants (322) were randomly assigned to one of the three diets: 1) low-fat, calorie-restricted, 2) Mediterranean, calorie-restricted, or 3) low-carbohydrate, non-restricted.  Calories in the low-fat and Mediterranean diets were “restricted” to 1800 per day for the men, 1500 for the women.  Average age of participants was 52, and average body mass index was 31.  [A 5-foot, 10-inch man weighing 216 pounds (98.2 kg) has a BMI of 31.]  Nearly all participants – 277 or 86% of the total – were men.  So there were only 45 women.  Forty-six participants had type 2 diabetes.

The low-fat diet was based on the American Heart Association guidelines of 2000: 30% of calories from fat [this isn’t very low], 10% of calories from saturated fat, cholesterol limited to 300 mg/day.  [The AHA revised their guidelines in 2006.]  Low-fat dieters ”were counseled to consume low-fat grains, vegetables, fruits, and legumes and to limit their consumption of additional fats, sweets, and high-fat snacks.”

The Mediterranean diet was based on the recommendations of Walter Willett and P.J. Skerrett as in their book, Eat, Drink, and be Healthy: The Harvard Medical School Guide to Health Eating.  Mediterranean dieters ate 2 fish meals per week, a handful of nuts daily, 30-45 grams of extra virgin olive oil per day, etc.  [One tablespoon of olive oil is 14 grams.]  The AHA states that “this diet reflects the current recommendations from the American Heart Association.”  There were no specific recommendations regarding alcohol in any of the diets.

The low-carb diet was based on  Atkins’ New Diet Revolution of 2002.  The goal was to provide 20 grams of carbohydrate per day for the 2-month induction phase, with a gradual increase to a maximum of 120 grams daily to maintain weight loss.  Total calories, protein, and fat were not limited.  “Participants were counseled to choose vegetarian sources of fat and protein….”

Whole grains were recommended for the low-fat and Mediterranean cohorts.

All participants worked at the same nuclear research facility in Dimona, Israel.  They were given careful instructions, initially and periodically, regarding the diet to which they were assigned.  Lunch is the main meal of the day in Israel, and they all ate lunch at the facility’s self-service cafeteria, which prompted them to choose the proper food items.  I assume they were told to maintain the diet when off-duty.  Adherence to the diets was assessed by a food-frequency questionnaire.

Findings

  • After 24 months, how many participants were still involved?  90% in the low-fat group, 85% in the Mediterranean, 78% in the low-carb.
  • There was little change in the usage of medications, and no significant differences among the groups.
  • Daily energy intake (calories or kcal) decreased from baseline levels significantly – about 450 calories – in all groups at 6, 12, and 24 months compared with baseline, with no significant differences among the groups in the amount of decrease.
  • All groups started with 51% of energy intake (calories) from carbohydrate.
  • At 24 months, the low-carb dieters were getting 40% of their daily calories as carbohydrates.  The other two groups were eating 50% of energy intake from carbs. [This still seems like a lot of carbs on the Atkins diet.  A gram of carbs has 4 calories.  The stated carbohydrate goal was a maximum of 120 grams of carbs daily, on a diet of 1800 calories.  So 120 grams of carbohydrate should be 27% of total daily calories.  At no point did the low-carb group reduce their average percentage of calories from carbohydrates under 40%.  OK, maybe be in the first two weeks but those data are not reported.  On an 1800 calorie diet, 40% of calories from carbs would be 180 grams.]
  • At 24 months, the low-carb dieters were getting 39% of their daily calories as fat.  The other two groups were in the 30-33% range.
  • Baseline fat intake for all groups was 31-32% of total calories, with saturated fat being 10% of the fat calories.
  • The low-fat cohort dropped their fat calories from 31 to 30% of total calories, which is essentially no change from baseline percentage.
  • At 24 months, the low-carbers were getting 22% of their daily calories from protein.  The other groups were at 19%.  [The low-carb Atkins diet is often criticized as having too much protein.]
  • Only the low-carb group made major changes in macronutrient composition of their diet.  Macronutrients are protein, fat, and carbohydrates.  This Atkins group increased saturated fat from 10 to 12% of total calories, reduced carbs from 51 to 40% of calories, increased protein from 19 to 22% of calories, and increased total fat from 32% to 39% or total calories.
  • All cohorts lost weight, but losses were greater in the low-carb and Mediterranean groups.  For the 272 participants who completed the full 24 months of intervention, the losses averaged 3.3 kg (7.3 lb) for the low-fat group, 4.6 kg (10.1 lb) for the Mediterraneans, and 5.5 kg (12.1 lb) for the low-carb group.
  • Among the 45 women, the low-fat group lost only 0.1 kg (0.22 lb), the Mediterraneans lost 6.2 kg (13.6 lb), and the low-carbers lost 2.4 kg (5.3 lb).  There were only 15, 20, and 10 women in these groups, respectively.
  • All groups had significant blood pressure reductions: about 4 mmHg systolic and 1 mmHg diastolic.
  • HDL cholesterol (the “good cholesterol”) increased in all groups, 8.4 mg/dl in the low-carb group, about 6.3 in the others.
  • LDL cholesterol (the “bad cholesterol”) fell 5.6 mg/dl in the Mediterraneans, 3.0 mg/dl in the low-carbers, and none in the low-fat group.  But these were not statistically significant differences between the groups.
  • The ratio of total to HDL cholesterol decreased for all groups, but the relative 20% decrease in the low-carb group was statistically significant compared to the 12% relative decrease in the low-fat group.  The ratio fell 16% in the Mediterranean group.  [The total/HDL ratio is thought to reflect risk of developing atherosclerotic complications.  You want it under 5 to 1, and 3.5 to 1 may be ideal.]
  • The level of high-sensitivity C-reactive protein decreased significantly only in the Mediterranean and low-carb cohorts.  [C-reactive protein is felt to be a marker of the systemic inflammation that has a role in atherosclerosis or hardening of the arteries.]
  • Thirty-six of the diabetics had adequate lab studies for analysis – about 12 in each diet group.  Only those in the Mediterranean group had a significant decrease in fasting glucose – 33 mg/dl.  The low-fat group had an increase.  Glycated hemoglobin decreased in all three groups although to a significant degree (0.9%) only in the low-carb group.  [High glycated hemoglobin levels reflect poor control of blood sugar levels in diabetics.]
  • Insulin levels decreased significantly in all three groups, diabetic or not.  [Abnormally high insulin levels are felt to have adverse health effects.]

Limitations of the study

  • Relatively few women, making it difficult to reliably generalize results to women.
  • Relatively few people with diabetes, making it difficult to reliably generalize results to people with diabetes.
  • Israeli gene pool?  Results not applicable to others?
  • No change in physical activity recommended to participants.  Increased exercise should enhance weight loss.

Take-Home Points

  • Caloric restriction leads to weight loss.
  • Mild degrees of weight loss reduce blood pressure.
  • In this study, the low-carb/Atkins and Mediterranean diets were more effective than the “low-fat” diet.
  • Atkins dieters can lose weight without counting calories, by limiting carbohydrate intake.
  • You gotta wonder if the low-carb group would have been even more successful if they had actually limited carbs to 120 grams daily.
  • It’s possible a lower-fat diet may have been more efficacious than the one utilized here.
  • This study did not enroll enough women to prove that a calorie-restricted Mediterranean diet is superior to low-fat and Atkins diets.  The greater weight loss – 13.6 pounds for Mediterranean versus 5.3 with Atkins – is suggestive and requires further study.
  • The average amounts of weight loss are not much when you think about the effort expended over 24 months of intervention.
  • These dieters reportedly reduced their daily caloric intake from baseline levels by about 450 calories, over the course of two years.  Yet they lost relatively little weight.  The numbers do not jive.  Most likely there is a problem with the methodology.  I doubt the average daily calorie deficit was as high as 450.
  • The Mediterranean diet seems to have been better for the people with diabetes.  Confirmatory studies are imperative.  Insulin resistance is an important factor in type 2 diabetes.  Monounsaturated fats, which are prominent in olive oil and the Mediterranean diet, are linked to improvement in insulin resistance in other studies.
  • For people who need to lose excess fat yet refuse to consciously restrict overall caloric  intake, the low-carb Atkins diet is a reasonable option.
  • The traditional Mediterranean diet has demonstrable long-term health benefits: longer lifespan, less cancer (colon, prostate, breast, uterus), reduction of cardiovascular disease, less dementia, and prevention of type 2 diabetes.  The Atkins diet cannot make those claims in 2008.

Steve Parker, M.D.

Reference:  Shai, Iris, et al.  Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet.  New England Journal of Medicine, 359 (2008): 229-241.

Additional information and critical analysis for health nuts like me:

Dr. Dean Ornish’s analysis in Newsweek online   Dr. Ornish is a leading low-fat diet advocate.

American Heart Association comments on the study in a July 19, 2008, news release

My additional comments:

The Mediterranean diet used in this study is based on Walter Willett’s 2001 book, Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating.  From the author:

I wrote this book to show you where the USDA Pyramid is wrong and why it is wrong.  I wanted to offer a new healthy eating guide based of the best scientific evidence, a guide that fixed the fundamental flaws of the USDA Pyramid and helps you make better choices about what you eat.  I also wanted to give you the latest information on new discoveries that shuould have profound effects on our eating patterns. 

Dr. Willett made a conscious decision not to call his new eating plan a Mediterranean diet.  Elsewhere in the book he notes that the Mediterranean diet pyramid promoted by Oldways Preservation and Exchange Trust is a good, evidence-based guide for healthy eating.  The entire book promotes Harvard’s Healthy Eating Pyramid, not the Mediterranean diet per se.

Harvard’s Healthy Eating Pyramid:

Harvard's Healthy Eating Pyramid

So were the Mediterranean dieters in the study at hand even following the Mediterranean diet?  The most glaring difference is Harvard’s lack of emphasis on olive oil.  Of lesser note is Harvard’s recommendation to eat white rice, white bread, potatoes, and refined-flour pasta only sparingly.  However, the researchers for this study directed Mediterranean diet participants to ingest 30-45 grams of olive oil per day.  After comparing the Harvard pyramid with the Oldways Mediterranean pyramid and other Mediterranean diet descriptions, it is fair to say the dieters here were indeed instructed on a Mediterranean diet.  In fact, the Mediterranean diet in this study is quite similar to the Advanced Mediterranean Diet.

Traditional healthy Mediterranean diet pyramid of Oldways Preservation and Exchange Trust:

Traditional healthy Mediterranean diet pyramid of Oldways Preservation and Exchange Trust

 

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June 22, 2009 · 2:00 AM

Do Vitamin D and Calcium Supplements Cut Risk of Diabetes?

Cliffs of Dover: Pure White Calcium Carbonate

Cliffs of Dover: Pure White Calcium Carbonate

Several studies have associated vitamin D and calcium intake with lower risk of developing type 2 diabetes.  After reading that the Institute of Medicine in 2010 will probably increase the recommended amounts of vitamin D for every one, I decided to review the literature pertinent to diabetes.

Over the last 10 years, studies have associated low blood levels of vitamin D with a higher risk of cardiovascular disease, death, type 2 diabetes, some cancers, infections, autoimmune diseases, frequent falls in the elderly, and dementia.

The Institute of Medicine (in the U.S.) currently recommends 200 IU (international units) per day for people under 50, 400 IU for people 50-70, with an upper intake level of 2,000 IU per day.  I assume those amounts refer to a combination of food (or supplements) and the vitamin D your skin makes (but how do we know that?). 

The new recommendation is expected to be around 1,000-2,000 IU per day.  It’s quite difficult to get close to that just with food.  With adequate sun exposure, we can make some vitamin D.  But the dermatologists have scared us out of the sun with horror stories of skin cancer.  I’ve seen some tragic cases in my own patients.  Skin covered with sunscreen doesn’t make vitamin D.  It can be difficult to get enough sun exposure, especially at higher latitudes in winter

I reviewed scientific articles pertinent to tyepe 2 diabetes via PubMed and list the best ones for you below.   The evidence in favor of using vitamin D and calcium supplements to prevent diabetes is weak, but may be correct. 

I found nothing to suggest that high vitamin D and calcium intake (whether food or supplements) helps control established cases of diabetes. 

Take-Home Points 

If you want to prevent type 2 diabetes with supplements, 1000 IU of vitamin D and 800-1000 mg of elemental calcium daily might help.  The evidence is not strong.  It might help; it might not.  But it’s unlikely to hurt.  Check with your personal physician first.  More studies are needed.  Calcium supplements are routinely recommended by expert nutrition panels for people over 60 to prevent osteoporosis.  The vitamin D supplement may be healthy in other ways.

Who, in particular, might want to prevent type 2 diabetes?  People with . . .

I’m sufficiently convinced about the nondiabetic vitamin D benefits that I’m going to start taking 1,000 IU per day.

Steve Parker, M.D.,

References:

Pittas, Anastassios, et al.  The effects of calcium and vitamin D supplementatinon on blood glucose and markers of inflammatin in nondiabetic adults.  Diabetes Care, 30 (2007): 980-9896.

Chowdhurry, T.A., et al.  Vitamin D and type 2 diabetes: Is there a link?  Primary Care Diabetes, April 21, 2009 (Epub ahead of print).

Pittas, Anastassios, et al.  Vitamin D and calcium intake in relation to type 2 diabetes in women.  Diabetes Care, 29 (2006): 650-656.

Knept, P., et al.  Serum vitamin D and subsequent occurrence of type 2 diabetes.  Epidemiology, 19 (2008): 666-671.

de Boer, I.H., et al.  Calcium plus vitamin D supplementation and hte risk of incident diabetes in the Womens’ health Initiative.  Diabetes Care, 31 (2008): 701-707. (Epub January 30, 2008).

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June 21, 2009 · 2:00 AM

Adverse Health Effects of Obesity

"I'm not fat, I'm chubby"

"I'm not fat, I'm chubby"

As a physician, I see many illnesses and conditions that are caused or aggravated by overweight and obesity.  Both terms refer to excess body fat; obesity is a greater degree of fat.

Body mass index (BMI) is used to define overweight and obesity.  Your BMI is your weight in kilograms divided by your height in meters squared.  A BMI between 18.5 and 25 is considered healthy.  BMIs between 25 and 30 are overweight.  Here’s an online BMI calculator.  For example, a 5-foot, 4-inch person enters obesity territory – BMI over 30 – when weight reaches 174 pounds (79 kilograms).  A 5-foot, 10-incher is obese starting at 208 pounds (94.5 kilograms).

People trying to lose excess fat typically have days when willpower, discipline, and commitment waver.  On those days, it can help to remember why they started this adventure in the first place.  The reasons for many involve improved health and longevity.  Even if you have just 20 pounds of excess fat to lose, it will often take twenty weeks.  Your weight-loss goal is one to one-and-a-half pounds a week. 

This race is won not by the swift, but by the slow and steady.

Here’s a laundry list of obesity-related conditions to remind you why you want to avoid obesity:

  • Premature death.  It starts at BMI of 30, with a major increase in premature death at BMI over 40.  The U.S. has 200,000 yearly deaths directly attributable to obesity.
  • Arthritis, especially of the knees.
  • Type 2 diabetes melllitus.  Eight-five percent of people with type 2 diabetes are overweight.
  • Increased cardiovascular disease risk, especially with an apple-shaped fat distribution as compared to pear-shaped.  Cardiovascular disease includes heart attacks, high blood pressure, strokes, and peripheral arterial disease (poor circulation).
  • Obstructive sleep apnea.
  • Gallstones are three or four times more common in the obese.
  • High blood pressure.  At least one third of cases are caused by excess body fat.  Every 20 pounds of excess fat raises blood pressure 2-3 points (mmHg).
  • Tendency to higher total and LDL cholesterol, higher triglycerides, while lowering HDL cholesterol.  These lipid changes are associated with hardening of the arteries – atherosclerosis – which can lead to heart attacks, strokes, and peripheral arterial disease.
  • Increased cancers.  Prostate and colorectal in men.  Endometrial, gallbladder, cervix, ovary, and breast in women.  Kidney and esophageal adenocarcinoma in both sexes.  Excess fat contributes to 14-20% of all cancer-related deaths in the U.S.  Over 550,000 people die from cancer in the U.S. yearly.  Twenty percent of us will die from cancer.
  • Strokes.
  • Low back pain.
  • Gout.
  • Varicose veins.
  • Hemorrhoids.
  • Blood clots in legs and lungs.
  • Surgery complications: poor wound healing, blood clots, wound infection, breathing problems.
  • Pregnancy complications: toxemia, high blood pressure, diabetes, prolonged labor, greater need for C-section.
  • Fat build-up in liver.
  • Asthma.
  • Low sperm counts.
  • Decreased fertility.
  • Delayed or missed diagnosis due to difficult physical examination or weight exceeding the limit of diagnostic equipment.

I hope you find this information motivational rather than depressing.  For those already obese, weight loss can significantly improve, alleviate, or prevent these conditions.  Many obesity-related medical conditions and metabolic abnormalities are improved with loss of just five or 10% of total body weight.  For instance, a 240 pound man with mild diabetes and high blood pressure may be able to reduce or avoid drug therapy by losing just 12 to 24 pounds.  He’s still obese, but healthier.

Steve Parker, M.D. 

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June 20, 2009 · 2:00 AM

Low-Carb Diet Beats Low-Fat, Calorie-Restricted Diet

Body mass index 38

Body mass index 38

I found one of the early studies (2003) demonstrating the effectiveness and safety of an Atkins-style diet in the severely obese.  Doctors traditionally have been hesitant to recommend the Atkins diet out of concern for tolerability and potential increased atherosclerosis complication such as heart attacks, strokes, and poor circulation.

Methodology

The study enrolled 132 subjects with an average body mass index of 43, including 77 blacks and 23 women.  39% had diabetes, 43% had metabolic syndrome.  They were randomly assigned to either . . .

  1. a low-carb diet without caloric restriction (carbohydrates limited to 30 gm/day; vegetables and fruits with high ratios of fiber to carbohydrate were recommended), or
  2. a low-fat, calorie-restricted diet. 

Subjects followed their diets for six months.  The researchers never specified, but I’m assuming the diabetics were all type 2. 

Results

The drop-out rate was equally high in both groups: only 79 subjects completed the study.  The low-carb group lost 5.8 kg (13 lb); the low-fat group lost 1.9 kg (4 lb).  Analysis included the drop-outs, for reasons unclear to me.  White subjects lost more weight than blacks: 13 versus 5 kg (29 versus 11 lb).  Total cholesterol, HDL cholesterol, and LDL cholesterol levels did not change significantly within or between groups.  [HDL usually rises on a low-carb diet.]   Triglycerides fell 20% in the low-carb group and 4% in the other group.  For subjects with diabetes, glucose levels fell 26 mg/dl in the low-carb group compared to 5 mg/dl in the low-fat group.  Uric acid levels didn’t change in either group.  [Elevated uric acid levels can cause gout.]  No significant adverse reactions attibutable to the diets were recorded in either group.  Glycosylated hemoglobin fell from 7.8 to 7.2% in the low-carb group, with no change in the low-fat group.   

Take-Home Points  

It’s a small study, so results may not be very accurate or generalizable to other populations.

In this cohort with a high prevalence of diabetes, the low-carb diet was more effective than the low-fat/calorie-restricted diet for weight loss, with no adverse lipid changes to suggest increased long-term cardiovascular risk.  The low-carb diet helped control diabetes. 

Steve Parker, M.D. 

Reference:  Samaha, Frederick, et al.  A low-carbohydrate as compared with a low-fat diet in severe obesity.  New England Journal of Medicine, 348 (2003): 2,074-2,081.

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