Category Archives: Protein

September 23, 2009 · 10:35 AM

What’s the Best Diet to Prevent Osteoporosis?

MedicalHappy Healthy Long Life, a blog by an anonymous “medical librarian,” has a thought-provoking article on the best diet to prevent osteoporosis: high in fruits and vegetables, low in animal proteins.

Osteoporosis is a common disease of the elderly, affecting women much more than men.  It causes thin, brittle bones that break easily.  You know all those little old ladies with broken hips?  Nearly all have osteoporosis. 

The standard prescription for prevention is weight-bearing exercise on a regular basis, and adequate intake of calcium and vitamin D.  The aforementioned blog post rejects the calcium recommendation, at least.

I haven’t reviewed this issue for many years and I just discovered Happy Healthy Long Life, so I have no opinion on validity of the post.

Steve Parker, M.D.

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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 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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May 11, 2009 · 12:00 AM

High- vs Low-Protein Weight-Loss Diet in Type 2 Diabetes

 

Mucho protein, amigo

Mucho protein, amigo

A high-protein weight-loss diet yielded greater reduction in LDL cholesterol in both sexes, and greater loss of abdominal fat in overweight type 2 diabetics, compared to a lower-protein diet.  Lower LDL cholesterol levels are associated with lower risk of heart attack.

This scientific study caught my eye because it utilized a high-monounsaturated fat diet for weight loss.  The Mediterranean diet is rich in monounsaturated fats, mostly from olive oil.

Researchers in Australia ran a study to determine the effect of high- versus lower-protein wieght loss diets on fat and lean tissue, glucose levels, and blood lipids.  For perspective, remember that a typical American diet has about 15% of calories from protein, 30% from fat, and 55% from carbohydrates.

Methodology

This was their high-protein diet:  28% protein, 42% CHO, 28% fat (8% saturated fatty acids, 12% monounsaturated fatty acids, 5% polyunsaturated fatty acids).

The low-protein diet:  16% protein, 55% CHO, 26% fat (8% saturated fatty acids, 11% monounsaturated fatty acids, 5% polyunsaturated fatty acids).

They studied 54 obese men (19) and women (35) with type 2 diabetes during 8 weeks of energy restriction (1,600 kcal) and 4 weeks of energy balance.  Body composition was determined by dual-energy X-ray absorptiometry at weeks 0 and 12.

Results

Average weight loss for both groups was 5 kg.  However, women on the HP diet lost significantly more total (5.3 vs 2.8 kg) and abdominal (1.3 vs 0.7 kg) fat compared with the women on the LP diet, whereas, in men, there was no difference in fat loss between diets (3.9 vs 5.1 kg).  Total lean mass decreased in all subjects independently of diet composition.  LDL cholesterol reduction was significantly greater on the HP diet (5.7%) than on the LP diet (2.7%).  Blood glucose levels were reduced 5 or 10% by both diet interventions.  Trigylcerides dropped 20% in both groups.  Insulin concentrations were reduced in both groups.  Subjects lose 2.1% lean mass overall, with no difference between the groups.

Conclusions of the Study Authors

Both dietary patterns resulted in improvements in the cardiovascular disease (CVD) risk profile as a consequence of weight loss. However, the greater reductions in total and abdominal fat mass in women and greater LDL cholesterol reduction observed in both sexes on the HP diet suggest that it is a valid diet choice for reducing CVD risk in type 2 diabetes.

Take-Home Points

This was a relatively small study, so results may not be widely applicable.

Substituting proteins for carbs doesn’t seem to be detrimental to people with type 2 diabetes needing to lose weight, and may be advantageous:  greater total and abdominal fat loss in women, greater reductions in LDL cholesterol for both sexes.   At least in the short run.

Nephrologists will be concerned that the higher-protein diet, if sustained long-term, could lead to kidney damage.

Current dogma is that the lower-carb (high-protein) dieters should have had lower blood glucose, triglycerides, and HgbA1c levels:  not seen here.

Calorie-restricted diets tend to lower glucose levels and improve lipids, despite diet composition.

Reference:  Parker, Barbara et al.  Effect of a High-Protein, High–Monounsaturated Fat Weight Loss Diet on Glycemic Control and Lipid Levels in Type 2 Diabetes.  Diabetes Care,  25 (2002): 425-430.    From CSIRO Health Sciences and Nutrition, Adelaide, Australia.

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