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.
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.
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.
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.