High Protein Diets- Do They Work??
Kelli Culler, Doctor of Pharmacy Candidate, University of Florida
Due to the increasing prevalence of obesity in our society, healthcare professionals are constantly driven to find new ways to help patients prevent many of the long-term complications of uncontrolled weight. Long-term complications may include hypertension, cardiovascular disease and type 2 diabetes which can all cause additional health risks. Researchers have looked at the differences between patients who followed different types of diets and the effects of the diet on food intake and weight control. This review attempts to look at high protein diets and the effects that they have on “weight loss, body composition, preservation of lean body mass, and improvement in several cardiovascular risk factors for up to 12 months.”
High protein diets (30% of total energy intake) were found to have an increased diet-induced thermogenesis (DIT), increased satiety, and higher sleeping metabolic rate than diets with lower protein content (10% of total energy intake). The success of many low carbohydrate diets may be explained by the higher protein intake. Over a 6 month period, subjects on a high protein, low carbohydrate diet lost an average of 7.26 pounds more than subjects on a low fat diet. This success is contributed to higher satiation and “lower spontaneous energy intake” or less impulse eating. The higher fat loss of low carbohydrate/high protein diets have been also linked to “decreased insulin concentrations with subsequent mobilization of fatty acids.”
What about long term success? Study reveals that one significant contributing factor to keeping weight off is regular contact with health professionals. The group of patients who had this support “regained less weight than the self-directed control group 30 months after a 6-month weight loss intervention.”
The effects of a high protein diet on cardiovascular risk. A 12 month trial reports that high protein diets account for the largest beneficial effects on HDL, triglycerides and blood pressure compared to lower protein diets, however, the results of total cholesterol and LDL were “less favorable.” The effects on LDL and total cholesterol may be attributed to lower fiber consumption in the high protein group. Two recent studies show that after one year, patients on higher protein diets had a significantly sustained reduction in cardiovascular risk factors, specifically fasting glucose levels, lipids, and CRP.
The effects of high protein intake on glycemic control. Benefits shown in several major studies include “improved insulin sensitivity or lower fasting insulin concentrations following dietary intervention.” While these results are promising, it is still not clear if these benefits are specifically from the high protein diet, weight loss, or a combination of the two. This study also notes that increased glucose metabolism and insulin sensitivity resulting in weight loss may counteract the harmful effects that amino acids may have on insulin sensitivity, however, this concept requires further investigation.
Potential detrimental effects of high-protein diets. While there has been no established upper limit for protein intake for patients of all health populations, it may be prudent to say that patients with renal insufficiency or risk factors for renal disease should use caution when starting high protein diets. The ADA currently recommends an upper limit of 20% daily protein intake until further long-term investigation is performed. Bone health may be another limiting factor to the amount of daily protein consumption, although more studies are needed in this area as well.
Information obtained in this review was found in the Current Opinion in Endocrinology, Diabetes & Obesity. Brehm, Bonnie J; D'Alessio, David A. Benefits of high-protein weight loss diets: enough evidence for practice? Current Opinion in Endocrinology, Diabetes & Obesity. 15(5):416-421, October 2008.