July 10, 2009 · 4:11 AM

Low-Glycemic-Index Eating Had No Effect on Control of Mild Type 2 Diabetes

Caprese salad

Caprese salad

A Canadian study last year found no overall effect on type 2 diabetes control by using a low-glycemic-index diet and lower-carbohydrate diet, although the low-glycemic-index diet did reduce post-meal glucose levels and C-reactive protein.

Background

For many years, a high-fat, low-carbohydrate diet was recommended for type 2 diabetics.  Then in 1979 the American Diabetes Association recommended a high-carb, low-fat diet.  Later, the ADA allowed more fat, mostly monounsaturated. 

The experts are still debating how much and what kind of carbohydrate people with diabetes should eat.  Recent years have seen a trend towards lower carbohydrate intake and lower-glycemic-index eating.  Much of the supportive evidence we have is based on short-term studies – six to 12 weeks. 

A Cochrane review in 2004 concluded that there was no high-quality data on the effectiveness of dietary treatment of diabetes.

The authors of the Canadian study at hand wrote:

Although almost everyone would agree that diet is the cornerstone of diabetes therapy, there is marked disagreement about what kind of dietary advice is best, particularly with respect to dietary carbohydrate.

We can put a man on the moon, but still aren’t sure what’s the best diet for people with diabetes despite years of experience and experimentation.

The Canadian researchers aimed to compare the effects of altered glycemic index and amount of carbohydrate on hemoglobin A1c, blood glucose, lipids, and C-reactive protein in men and women with type 2 diabetes.

Methodology

162 subjects with mild diabetes, 35-75 years old, managed by diet alone, were randomly assigned to one of three diet groups:

  1. high-carb, high-glycemic-index (“high-GI“): 47% of calories from carb, 31% of cals from fat, glycemic index 63
  2. high-carb, low-glycemic-index (“low-GI“): 52% of cals from carb, 27% of cals from fat, glycemic index 55
  3. low-carb, high-monounsaturated fat (“low-CHO“): 39% of cals from carb, 40% of cals from fat, glycemic index 59

Average body mass index was 31 (mildly obese); average weight 83 kg (183 lb).  The study lasted one year, a major strength of the study.

Results One Year Later

Hemoglobin A1c rose from 6.1% to 6.3%, with no difference between the various diet groups.  There were no differences in insulin levels, whether fasting or two hours after an oral glucose tolerance test.  Blood sugar levels after a glucose tolerance test were 7% lower with the low-GI diet compared to the other diet groups.  No difference in LDL cholesterol levels.  Little effect on triglycerides and HDL cholesterol.  No differences in weight.  C-reactive protein in the high-GI group fell from3.34 mg/L to 2.75.  C-reactive protein in the low-GI group fell from 2.64 to 1.95.  [All these C-reactive protein readings are in the normal range.]        

Comments

Nearly all the people with diabetes I encounter are very different from this study cohort: they are on drug therapy for diabetes.  So the results here don’t  necessarily apply to the more typical cases of moderate or severe diabetes that require one or more glucose-control drugs. 

Low-carb diet advocates can justifiably argue that the carb intake was still too high, and that’s why their numbers weren’t better.  Vernon and Eberstein in their book, Atkins Diabetes Revolution, note that many people with type 2 diabetes will have to limit carboydrates (“net carbs”) to 40-60 grams a day.  In the study at hand, the low-carb diet aimed for 39% of calories from carbohydrates.  On a 2000-calorie diet, that’s 195 grams – a far cry from 60 grams.      

Low-Gi advocates also can justifiably argue that the glycemic index was not low enough to make a difference.  The researchers admit that the test diet reductions in carb intake and glycemic index were “modest.”  Perhaps they thought that more drastic reductions were unsustainable.

Attempts to control diabetes with low-carb or low-glycemic-index eating should make more dramatic changes.

The low-glycemic-index diet lowered two-hour glucose levels on the glucose tolerance tests.  The authors state that this parameter is a better indicator of heart disease risk – lower in this case – than are fasting glucose levels.  Findings suggests improvements in insulin resistance and/or pancreas beta cell function.  This finding may have no real-world clinical significance: remember that hemoglobin A1c levels were the same across all groups. 

The changes in C-reactive protein just don’t seem clinically significant to me (nor to an editorialist in the same journal issue).

The aforementioned editorialist, Dr. Xavier Pi-Sunyer, had an interesting comment:

This finding suggests that we must be careful about disrupting subjects’ or patients’ diets with radical , doctrinaire changes that may actually be counterproductive.  Furthermore, the diets had carbohydrate contents that varied from 39% to 52% of energy intake, and yet this variability had no effect on the subjects’ HbA1c.  This finding confirms previous reports that the proportion of carbohydrate in the diet is not very important in determining the concentration of fasting blood glucose and that variations of 10% to 15% of total calories make little difference to overall control in patients with early type 2 diabetes.

I would emphasize “. . . in patients with early type 2 diabetes.”

A Mediterranean-style diet, then, could be just as effective as, if not better than, all the other “diabetic diets” out there.

Steve Parker, M.D.

References:  Wolever, Thomas, et al.  The Canadian Trial of Carbohydrates in Diabetes (CCD), a 1-y controlled trial of low-glycemic-index dietary carbohydrate in type 2 diabetes: no effect on glycated hemoglobin but reduction in C-reactive protein.  American Journal of Clinical Nutrition, 87 (2008); 114-125.

Additional Resource:  Michael R. Eades, M.D.  Making worthless data confess.  The Blog of Michael R. Eades, December 13, 2008.  Accessed July 10, 2009.  [Highly critical analysis from a leading low-carb, high-protein advocate.]

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July 5, 2009 · 2:00 AM

ADA Now Says Low-Carb Diets OK for Overweight Type 2 Diabetics

CB037166Eighty-five percent of type 2 diabetics are overweight or obese.  Overweight either causes or aggravates many cases of diabetes.

For the last quarter-century, many U.S. government agencies and healthcare organizations have advocated a low-fat diet for overweight people, including type 2 diabetics.  Recent studies have documented that low-carbohydrate diets can also be effective in weight loss.  Low-carb diets replace carbohydrates with either fats or proteins, or both.  The A to Z Weight Loss Study compared the Atkins, Ornish, LEARN, and Zone diets in 311 overweight pre-menopausal women.  The Atkins group tended to lose a bit more weight. Changes in lipid profiles, waist-hip ratios, fasting insulin and glucose levels, blood pressure, and percentage of body fat were comparable or better with Atkins versus the other diets.

The Amerian Diabetes Association now gives the go-ahead for use of low-carb diets as a weight-control method for type 2 diabetics.  Previously, the organization had recommended against diets that restrict carbohydrates to less than 130 grams daily.  (A baked potatoe without the skin has 30 grams.)  Understand that the ADA does not endorse low-carb diets for weight loss or diabetes management.  They simply say that either low-carb or low-fat calorie-restricted diets might be effective for up to one year.

I caution you that low-carb diets may be deficient in fiber, minerals, vitamins, and phytonutrients that may be very beneficial in terms of long-term health and longevity.

The tide has been turning against low-fat diets for the last six years.

Steve Parker, M.D.

Reference: American Diabetes Association.  Clinical Practice Recommendations 2008.  Diabetes Care, 31 (2008): S61-S78.

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July 4, 2009 · 2:00 AM

ABC News Outlines Healthy Components of the Mediterranean Diet

Happy Birthday, USA!

Happy Birthday, USA!

ABC News (online) June 24, 2009, published a well-done, detailed and balanced article on the various components of the traditional Mediterranean diet, such as fish, legumes, fruits and vegetables.  Lots of pretty pictures, too.  If you need a review, click here to read it. 

Steve Parker, M.D.

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July 3, 2009 · 2:00 AM

A Chance to Cut is a Chance to Cure

"Has anybody seen my pen?"

"Has anybody seen my pen?"

Gastric bypass is the most common bariatric surgery in the U.S.  The odds of dying from that procedure are roughly 1 in 200.  Thousands of people sign on the dotted line for it every year.  Why do they take that risk?

A recent study out of Sweden shows that people who undergo various bariatric surgeries reduce their risk of death over the next 11 years by 25%.

In the Swedish Obese Subjects Study, 2010 subjects underwent bariatric surgery and 2037 received conventional treatment.  Overall mortality was recorded over the next 11 years.  Only three of the subjects were lost to follow-up (unknown whether alive or not).  The average body mass index (BMI) for all subjects was 41.

Out of the conventional treatment group, 126 died.  In the surgery group, only 101 died.  Average weight change in the conventional treatment group was up or down only 2%.  People in the surgery group were given one of three operations: gastric bypass, vertical-banded gastroplasty, or banding.  After 10 years, average weight loss of the groups was 25%, 16%, and 14%, respectively.

Over the course of 11 years, people in the surgery group had 25% less chance of dying when compared to the conventional treatment group.  The most common causes of death were heart attacks and cancer.

Even better results were found back in the U.S.  Researchers in Utah looked at mortality rates of 7925 patients who had undergone gastric bypass surgery between 1984 and 2002.  They compared death rates to a control group (also 7925 people) of obese people who applied for driver’s licenses.  Subjects were matched for sex, body mass index, and age.  Average BMI of the surgical group was 45.

Over the course of seven years, there were 321 deaths in the control group and 213 in the surgery group.  Deaths from any cause were reduced by 40% in the surgery group, compare to the control group.  Surgery patients had less death from cardiovascular disease, diabetes, and cancer.

Surgery is definitely a roll of the dice.  Now you know why people play the game.

Steve Parker, M.D.

References:

Sjostrom, Lars, et al.  Effects of Bariatric Surgery on Mortality in Swedish Obese Subjects.  New England Journal of Medicine, 357 (2007):  741-752.

Adams, Ted, et al.  Long-Term Mortality after Gastric Bypass Surgery.  New England Journal of Medicine, 357 (2007): 753-761. 

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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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