Abstract
The recognized benefits of a higher protein diet on muscle mass and strength in older adults are tempered by concerns of the potentially negative cardiometabolic impact of dietary sources of animal protein. The aim of this study was to explore the cardiometabolic impact of 2 weight reduction diets: a higher protein diet, providing balanced portions of lean beef and pork throughout the day, vs. a diet following the Recommended Daily Allowance level of protein in obese middle-aged and older adults. Data from Measuring Eating, Activity and Strength: Understanding the Response-Using Protein and Protein Optimization in Women Enables Results-Using Protein were combined for the present analysis. Subjects were randomly assigned to a 6-month weight loss diet (500kcal deficit) and prescribed a Recommended Daily Allowance level of protein (0.8g protein/kg BW), control group, or a higher level of protein (1.2g protein/kg BW), protein group. For the protein group, lean, high-quality protein was evenly distributed between meals or balanced throughout the day (30g protein/meal). The following cardiometabolic markers were quantified by nuclear magnetic resonance spectroscopy: lipids, lipoproteins, GlycA, trimethylamine-N-oxide, betaine, branched-chain amino acids, and lipoprotein insulin resistance index scores. In both groups (control [n=27] and protein [n=53]), there were significant (P≤.05) changes from baseline in weight loss (-6.2% and -7.2%), distance walked (+53.1 and+75.0meters), and fasting plasma glucose (-7.5 and -6.2mg/dL), respectively. At endpoint, protein group had significantly (P≤.05) lower triglycerides (-17.3mg/dL), large very-low-density lipoprotein particle concentration (VLDL-P; -1.2nmol/L), total low-density lipoprotein particle concentration (LDL-P; -67.8nmol/L), small LDL-P (-59.4 nmol/L) and lipoprotein insulin resistance index (-5.9), whereas control group had significantly (P≤.05) lower GlycA (-13.1μmol/L), total VLDL-P (-7.9nmol/L), and small VLDL-P (-7.0nmol/L). Differences between groups were observed for small VLDL-P (P=.02) and protein intake (P<.0001). These findings suggest that a hypocaloric diet with either traditional (0.8g/kg BW/d) or higher protein (1.2g/kg BW/d; predominantly from lean red meat) content improves risk markers of cardiovascular disease and type II diabetes in obese middle-aged and older adults. Both diets were also associated with improved physical function, and neither had an adverse impact on cardiometabolic outcomes.
Highlights
Dietary intake of high-quality protein that is both ample and balanced has many known benefits for older adults, including promotion of muscle protein synthesis,[1] preservation of lean mass, muscle strength, and function,[2,3] higher bone mineral density,[4,5] and improved markers of glucose metabolism[6]; it may reduce fracture risk,[7] inflammation, and oxidative stress.[8]
Quantity, and timing of protein intake during weight reduction may favor these outcomes.[12,13]. This conclusion is supported by our findings that high-quality protein, above the Recommended Daily Allowance (RDA) and balanced throughout the day, benefits physical function during obesity reduction in functionally limited older adults[14] and by a recent review/meta-analysis[15] showing a protein benefit for preservation of lean mass during weight reduction
We found no baseline differences between control and protein groups for age, gender, race, marital status, and education; body weight, body mass index (BMI), and reported intakes of protein
Summary
Dietary intake of high-quality protein that is both ample and balanced has many known benefits for older adults, including promotion of muscle protein synthesis,[1] preservation of lean mass, muscle strength, and function,[2,3] higher bone mineral density,[4,5] and improved markers of glucose metabolism[6]; it may reduce fracture risk,[7] inflammation, and oxidative stress.[8]. Loss of lean muscle mass and strength in combination with obesity is a multiplier of detrimental health effects in mid- and later-life. It markedly reduces physical function,[9,10] and accelerates the development of type II diabetes and cardiovascular disease (CVD).[11] Effective treatment of obesity in middle-aged and older adults requires preferential reduction of adipose tissue while maintaining lean mass. The recognized benefits of a higher protein diet on muscle mass and strength in older adults are tempered by concerns of the potentially negative cardiometabolic impact of dietary sources of animal protein
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