Protein for Weight Loss

A review of

Huang G, Pencina K, Li Z, Apovian CM, Travison TG, Storer TW, Gagliano-Jucá T, Basaria S, Bhasin S. Effect of Protein Intake on Visceral Abdominal Fat and Metabolic Biomarkers in Older Men With Functional Limitations: Results From a Randomized Clinical Trial. J Gerontol A Biol Sci Med Sci. 2021 May 22;76(6):1084-1089. doi: 10.1093/gerona/glab007. PMID: 33417663; PMCID: PMC8140050.

By Dr. Bryan Stephens

Summarized Review Conclusions

High protein diets have gained more popularity over the years and many look at it as a way to help with weight loss. This article looked specifically on how the higher protein diets effected the visceral fat (fat around the organs) in older men. They found that a higher protein diet decreased the visceral fat in those men. This is promising as weight loss continues to be a high priority in our society as the overall obesity rates have continued to rise. With the increase of weight gain in our society, we have seen the impact it has had on overall health ranging from cardiovascular disease to stroke and diabetes. While there is no short cut to health, increasing healthy protein consumption can be a tool used to help.

“Protein intake >RDA decreased [Visceral Adipose Tissue] in functionally limited older men but did not improve cardiovascular disease risk markers.”

“There was a significant effect of protein level on [Visceral Adipose Tissue] area over 6 months.”

Introduction to the Research

Aging is linked to a decline in muscle mass, strength, and physical function. High-protein diets and anabolic agents like testosterone are being studied to counteract this loss. Recently, high-protein diets have gained attention for their potential to improve body composition and metabolic health by influencing hormones, thermogenesis, gluconeogenesis, and muscle protein synthesis. These diets have shown benefits in reducing adiposity, particularly when combined with exercise in overweight or obese adults. However, studies on the relationship between protein intake and cardiovascular disease risk have yielded conflicting results, and concerns exist about the safety of high-protein diets, especially due to the association of branched-chain amino acids with insulin resistance and diabetes. The mixed findings may be attributed to variations in study populations, diet duration, protein sources (animal vs. vegetable), and the definition of “high” versus “low” protein. Some studies used calorie-restricted diets, while others provided isocaloric diets. Therefore, the impact of high-protein diets on cardiometabolic health remains uncertain.

Research Methodology

“The participants were community-dwelling men, aged ≥65 years, with moderate physical function limitation, whose average daily protein intake was ≤0.8 g/kg/day (RDA). We excluded men with prostate cancer, severe lower urinary tract symptoms, untreated sleep apnea, myocardial infarction, or stroke within 6 months, or erythrocytosis (14). Men with diabetes requiring insulin or A1c > 8%, were excluded.”

“Daily energy and protein intakes were apportioned between prepackaged meals, protein or carbohydrate (placebo) supplements, and discretionary food allowances (15). Packaged meals with individualized protein and energy contents were supplied by Personal Chef to Go, Mechanicsville, VA, and provided 0.7 g/kg/day protein and 80% of daily energy requirements. Discretionary foods (fruits/vegetables, coffee/tea, alcoholic beverages, and other foods) provided an additional 0.1 g/kg/day of protein and 15% of energy. The difference between the prescribed protein and energy intakes and protein and energy contents of packaged meals was made up by protein or carbohydrate supplements. Participants received their daily protein allotment through packaged meals (0.7 g/kg/day), supplement (0 g/kg/day for control and 0.5 g/kg/day for higher protein group), and discretionary foods (0.1 g/kg/day). Participants in the 1.3 g/kg/day group received a supplement containing 0.5 g/kg/day of casein and whey protein mix, bringing their protein intake to 1.3 g/kg/day; the control group received a supplement containing 0.5 g/kg/day of carbohydrate powder. Twenty percent of daily energy intake was provided as breakfast, 40% as lunch, and 40% as dinner. Energy and protein contents of each participant’s individualized diet were standardized by providing packaged meals and supplements. Daily energy requirement was calculated using Dietary Reference Intake equation plus an activity factor (16). A 7-day supply of packaged food was picked up by participants or was home delivered. Participants received 1260 mg calcium, 1000-IU vitamin D3, and a multivitamin daily.”

Research Findings

“There was a significant effect of protein level on VAT area over 6 months. Men randomized to 1.3 g/kg/day protein had a significantly greater decrease from baseline in VAT area than those randomized to 0.8 g/kg/day protein (between-group difference: −17.3 cm2, 95% CI, −29.7 to −4.8 cm2, p = .008). There was no significant effect of protein level on fasting insulin, fasting glucose or HOMA-IR, leptin, adiponectin, IL-6, and hs-CRP over 6 months. The changes from baseline in these biomarkers did not differ among men assigned to 0.8 or 1.3 g/kg/day protein groups (Table 2), regardless of whether they received testosterone or placebo.

Testosterone administration was associated with a decrease in VAT area compared to placebo, regardless of protein intake; however, the between-group difference did not reach statistical significance (between-group difference: −11.6 cm2, 95% CI: −0.58 to 23.7 cm2, p = .06). Men randomized to testosterone had greater reductions in leptin levels than those randomized to placebo (between-group difference: −9.75 ng/mL, 95% CI: −14.8 to −4.75 ng/mL, p < .001), regardless of protein intake. There was no significant change from baseline in fasting insulin and glucose, HOMA-IR, adiponectin, hs-CRP, and IL-6 levels in men randomized to testosterone compared to placebo, regardless of protein intake.”

Research References

As always with these reviews, these are my takeaways from the article and I encourage you to read the article in its entirety. The references used in this article by the authors of this article are listed here.

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