Search

Background This narrative review describes foundational and emerging evidence of how dietary protein intakes may influence muscle-related attributes of older adults. Methods PubMed was used to identify pertinent research. Results Among medically stable older adults, protein intakes below the recommended dietary allowance (RDA) (0.8 g/kg body weight [BW]/d) exacerbate age-related reductions in muscle size, quality, and function. Dietary patterns with total protein intakes at or moderately above the RDA, including one or preferably more meals containing sufficient dietary protein to maximize protein anabolism, promote muscle size and function. Some observational studies suggest protein intakes from 1.0 to 1.6 g/kg BW/d may promote greater muscle strength and function more so than muscle size. Experimental findings from randomized controlled feeding trials indicate protein intakes greater than the RDA (averaging ~1.3 g/kg BW/d) do not influence indices of lean body mass or muscle and physical functions with non-stressed conditions, but positively influence changes in lean body mass with purposeful catabolic (energy restriction) or anabolic (resistance exercise training) stressors. Among older adults with diagnosed medical conditions or acute illness, specialized protein or amino acid supplements that stimulate muscle protein synthesis and improve protein nutritional status may attenuate the loss of muscle mass and function and improve survival of malnourished patients. Observational studies favor animal versus plant protein sources for sarcopenia-related parameters. Conclusions Quantity, quality, and patterning of dietary protein consumed by older adults with varied metabolic states, and hormonal and health status influence the nutritional needs and therapeutic use of protein to support muscle size and function. [ABSTRACT FROM AUTHOR]

Background: The 2018 Physical Activity Guidelines Advisory Committee Scientific Report provides the evidence base for the Physical Activity Guidelines for Americans, 2nd Edition. Methods: The 2018 Physical Activity Guidelines Advisory Committee addressed 38 questions and 104 subquestions selected for their public health relevance, potential to inform public policies and programs, maturity of the relevant science, and applicability to the general US population. Rigorous systematic literature searches and literature reviews were performed using standardized methods. Results: Newly described benefits of physical activity include reduced risk of excessive weight gain in children and adults, incidence of 6 types of cancer, and fall-related injuries in older people. Physical activity is associated with enhanced cognitive function and mental health across the life span, plus improved mental health and physical function. There is no threshold that must be exceeded before benefits begin to accrue; the accrual is most rapid for the least active individuals. Sedentary time is directly associated with elevated risk of all-cause and cardiovascular mortality, incident cardiovascular disease and type 2 diabetes, and selected cancer sites. A wide range of intervention strategies have demonstrated success in increasing physical activity. Conclusion: The 2018 Physical Activity Guidelines Advisory Committee Scientific Report provides compelling new evidence to inform physical activity recommendations, practice, and policy. [ABSTRACT FROM AUTHOR]

Background. Higher protein diets are promoted for effective weight loss. Striated tissues in omnivorous diets contain high-quality protein, but limited data exist regarding their effects on bone. Methods. To examine the effects of energy restriction--induced weight loss with higher protein omnivorous diets versus lower protein vegetarian diets on bone mineral density in overweight postmenopausal women, two randomized controlled feeding studies were conducted. In Study 1.28 women consumed 750 kcal/day energy deficit diets with 18% energy from protein via lacto-ovo vegetarian sources (normal protein, n = 15) or 30% energy from protein with 40% of protein from lean pork (higher protein, n = 13, omnivorous) for 12 weeks. In Study 2, 54 women consumed their habitual diet (control, n = 11) or 1,250 kcal/day diets with 16% energy from nonmeat protein sources (n = 14) or 26% energy from protein, including chicken (n = 15) or beef (n = 14) for 9 weeks. Results. Study I: With weight loss (normal protein -11.2%, higher protein -10.1%), bone mineral density was not significantly changed in normal protein (-0.003 [+ or -] 0.003 g/[cm.sup.2], -0.3 %) but decreased in higher protein (- 0.0167 [+ or -] 0.004 g/[cm.sup.2], -1.4%, group-by-time p < .05). Study 2: The control, nonmeat, chicken, and beef groups lost 1.5%, 7.7%, 10.4%, and 8.1% weight and 0.0%, 0.4%, 1.1%, and 1.4% bone mineral density, respectively. The change of bone mineral density was significant for chicken and beef compared with the control (group-by-time, p < .05). Markers of calcium metabolism and bone homeostasis in blood and urine were not changed over time or differentially affected by diet. Conclusion. Consumption of higher protein omnivorous diets promoted decreased bone mineral density after weight loss in overweight postmenopausal women. Key Words: Protein--Weight loss--Bone mineral density. doi: 10.1093/geron/glq083

The systematic review presented here assessed the effects of energy restriction (ER) and exercise (EX) on fat-free mass (FFM) in overweight and obese middle-aged and older adults. PubMed was searched using the key words 'weight loss or energy restriction' AND 'skeletal muscle or body composition,' with limitations set for 'human' and 'middle-aged and aged.' Results from 52 studies are reported as the percentages of EX (mainly aerobic training), ER, or ER+EX groups that had a specified change in body weight and FFM, since insufficient data were available for a meta-analysis. The EX groups had modest body weight and FFM changes. Eighty-one percent and 39% of the ER and ER+EX groups, respectively, lost [greater than or equal to] 15% of body weight as FFM. These findings suggest that exercise is an effective tool to help men and postmenopausal women aged [greater than or equal to] 50 years, with a BMI greater than 25 kg/[m.sup.2]preserve FFM after moderate ER-induced weight loss, which is important for combating sarcopenic obesity. Key words: aging, body composition, exercise, muscle loss, weight loss doi: 10.1111/j.1753-4887.2010.00298.x

Inclusion of dietary protein in meals and beverages affects the hepatic synthesis of the protein albumin. Besides dietary protein, several factors can influence albumin metabolism and affect plasma albumin. The role of aging in albumin synthesis is unclear. Recent research documents that albumin synthesis rate is influenced comparably in younger and older adults by dietary protein ingestion and changes in dietary protein quantity. This emphasizes the importance for all adults to consume an adequate amount of dietary protein.

Resistance exercise training helps older people treat sarcopenia. The consumption of diets that include sources of high-quality protein and total protein intakes that are moderately above the recommended dietary allowance of 0.8 g x [kg.sup.-1] x [d.sup.-1] while regularly performing resistance exercises can help older people retain or increase whole-body fat-free mass and muscle mass. Limited research suggests that protein-enriched nutritional supplements do not influence training-induced improvements when adequate dietary protein is consumed. Key words: aging, fat-free mass, muscle hypertrophy, nutritional supplementation, strength training

The aim of this study was to assess the effects of nutrient ingestion, dietary protein intake, age, and sex on the fractional synthesis rate (FSR) of albumin. Thirty-six healthy free-living individuals (8 females and 10 males aged 21-43 y and 9 females and 9 males aged 63-79 y) completed three 18-d periods of controlled feeding with protein intakes of 125% (P125, 1.00 g protein x [kg.sup.-1] x [d.sup.-1]), 94% (P94, 0.75 g protein x [kg.sup.-1] x [d.sup.-1]), and 63% (P63, 0.50 g protein x [kg.sup.-1] x [d.sup.-1]) of the recommended dietary allowance. On d 12 of each trial, postabsorptive (PA) serum albumin concentration was determined and PA and postprandial (PP) albumin FSR were estimated from the rate of L-[1-[sup.13]C] leucine incorporation into plasma albumin during an 8-h infusion. There were no age-related differences in PA and PP albumin FSR. Albumin FSR was higher PP than PA (P < 0.0001), and the increase in albumin FSR from PA to PP was smaller as dietary protein intake decreased from P125 to P94 and P63 (P< 0.05). Independent of protein intake, males had a higher albumin FSR (P< 0.05) and a greater increase in albumin FSR with feeding (P < 0.05). There was no age or dietary protein effect on serum albumin concentrations, but males had higher albumin concentrations than females (P < 0.0001). These results show that older persons are responsive to nutrient ingestion and dietary protein-related changes in albumin FSR. The greater albumin synthesis rate in males might contribute to a higher albumin concentration set point.

Many older people experience changes in appetite and consume marginal or inadequate dietary protein. This study was designed to examine the appetitive responses to habitual protein intakes that span the range of adequacy in younger and older men. Twenty-two men (12 younger, aged 21-43 y and 10 older, aged 63-79 y) completed, in random order, three 18-d trials that involved consumption of individualized, isoenergetic menus providing 1.00, 0.75, and 0.50 g protein * kg B[W.sup.-1] * [d.sup.-1], which were 125% (trial P125), 94% (trial P94), and 63% (trial P63) of the Recommended Dietary Allowance for protein. Near the end of each trial, the subjects recorded appetitive sensations hourly throughout one day using a visual analogue scale. Independent of age, ratings of hunger were lower for P125 (1.3 [+ or -] 0.5 cm) than P94 (1.8 [+ or -] 0.8 cm)and P63 (1.8 [+ or -] 0.6 cm)(P = 0.037), and desire to eat was lower during the P125 trial (1.4 [+ or -] 0.5 cm), compared with the P63 trial (2.1 [+ or -] 0.7 cm) (P = 0.003), and P94 (1.8 [+ or -] 0.7 cm) was not different when compared with P63 and P125. Protein intake did not influence fullness. These results show that younger and older men who consume inadequate protein experience appetite changes that may promote increased food intake.