Heather J. Leidy

Higher Protein Intake Preserves Lean Mass and Satiety with Weight Loss in Pre-obese and Obese Women

Objective: To examine the effects of dietary protein and obesity classification on energy‐restriction‐induced changes in weight, body composition, appetite, mood, and cardiovascular and kidney health.

Dietary Protein and Resistance Training Effects on Muscle and Body Composition in Older Persons

The regular performance of resistance exercises and the habitual ingestion of adequate amounts of dietary protein from high-quality sources are two important ways for older persons to slow the progression of and treat sarcopenia, the age-related loss of skeletal muscle mass and function. Resistance training can help older people gain muscle strength, hypertrophy muscle, and increase whole body fat-free mass. It can also help frail elderly people improve balance and physical functioning capabilities. Inadequate protein intake will cause adverse metabolic and physiological accommodation responses that include the loss of fat-free mass and muscle strength and size. Findings from controlled feeding studies show that older persons retain the capacity to metabolically adjust to lower protein intakes by increasing the efficiency of nitrogen retention and amino acid utilization. However, they also suggest that the recommended dietary allowance of 0.8 g protein · kg−1 · d−1 might not be sufficient to prevent subtle accommodations and blunt desired changes in body composition and muscle size with resistance training. Most of the limited research suggests that resistance training-induced improvements in body composition, muscle strength and size, and physical functioning are not enhanced when older people who habitually consume adequate protein (modestly above the RDA) increase their protein intake by either increasing the ingestion of higher-protein foods or consuming protein-enriched nutritional supplements.

Beneficial effects of a higher-protein breakfast on the appetitive, hormonal, and neural signals controlling energy intake regulation in overweight/obese, “breakfast-skipping,” late-adolescent girls

Background: Breakfast skipping is a common dietary habit practiced among adolescents and is strongly associated with obesity. Objective: The objective was to examine whether a high-protein (HP) compared with a normal-protein (NP) breakfast leads to daily improvements in appetite, satiety, food motivation and reward, and evening snacking in overweight or obese breakfast-skipping girls. Design: A randomized crossover design was incorporated in which 20 girls [mean ± SEM age: 19 ± 1 y; body mass index (in kg/m2): 28.6 ± 0.7] consumed 350-kcal NP (13 g protein) cereal-based breakfasts, consumed 350-kcal HP egg- and beef-rich (35 g protein) breakfasts, or continued breakfast skipping (BS) for 6 d. On day 7, a 10-h testing day was completed that included appetite and satiety questionnaires, blood sampling, predinner food cue–stimulated functional magnetic resonance imaging brain scans, ad libitum dinner, and evening snacking. Results: The consumption of breakfast reduced daily hunger compared with BS with no differences between meals. Breakfast increased daily fullness compared with BS, with the HP breakfast eliciting greater increases than did the NP breakfast. HP, but not NP, reduced daily ghrelin and increased daily peptide YY concentrations compared with BS. Both meals reduced predinner amygdala, hippocampal, and midfrontal corticolimbic activation compared with BS. HP led to additional reductions in hippocampal and parahippocampal activation compared with NP. HP, but not NP, reduced evening snacking of high-fat foods compared with BS. Conclusions: Breakfast led to beneficial alterations in the appetitive, hormonal, and neural signals that control food intake regulation. Only the HP breakfast led to further alterations in these signals and reduced evening snacking compared with BS, although no differences in daily energy intake were observed. These data suggest that the addition of breakfast, particularly one rich in protein, might be a useful strategy to improve satiety, reduce food motivation and reward, and improve diet quality in overweight or obese teenage girls. This trial was registered at clinicaltrials.gov as NCT01192100.

Dietary protein and muscle in older persons.

Purpose of reviewThe purpose of this study is to highlight recent advances in nutrition and protein research that have the potential to improve health outcomes and status in ageing adults. Recent findingsThe beneficial effects of dietary protein on muscle health in older adults continue to be refined. Recent research has bolstered support for moderately increasing protein consumption beyond the current Recommended Dietary Allowance by adopting a meal-based approach in lieu of a less specific daily recommendation. Results from muscle protein anabolism, appetite regulation and satiety research support the contention that meeting a protein threshold (approximately 30 g/meal) represents a promising strategy for middle-aged and older adults concerned with maintaining muscle mass while controlling body fat. SummaryOptimizing dietary protein intake to improve health requires a detailed consideration of topics including muscle protein anabolism, appetite control and satiety. Although each area of research continues to advance independently, recent collaborative and translational efforts have highlighted broad, translational consistencies related to the daily distribution and quantity of dietary protein.

The addition of a protein-rich breakfast and its effects on acute appetite control and food intake in 'breakfast-skipping' adolescents

Background:Breakfast skipping (BS) is closely associated with overeating (in the evening), weight gain and obesity. It is unclear whether the addition of breakfast, with emphasis on dietary protein, leads to better appetite and energy intake regulation in adolescents.Objective:The purpose of the study was to examine the impact of addition of a normal-protein (PN) breakfast vs protein-rich (PR) breakfast on appetite and food intake in ‘breakfast-skipping’ adolescents.Subjects and Design:A total of 13 adolescents (age 14.3±0.3 years; body mass index percentile 79±4 percentile; skipped breakfast 5±1 × per week) randomly completed 3 testing days that included a PN (18±1 g protein), PR (48±2 g protein) or BS. Breakfast was 24% of estimated daily energy needs. Appetite, satiety and hormonal responses were collected over 5 h followed by an ad libitum lunch and 24-h food intake assessments.Results:Perceived appetite was not different following PN vs BS; PR led to greater reductions vs BS (P<0.01) and PN (P<0.001). Fullness was greater following both breakfast meals vs BS (P<0.01) but was not different between meals. Ghrelin was not different among treatments. Greater PYY concentrations were observed following both breakfast meals vs BS (P<0.01) but was not different between meals. Lunch energy intake was not different following PN vs BS; PR led to fewer kcal consumed vs BS (P<0.01) and PN (P<0.005). Daily food intake was not different among treatments.Conclusions:Breakfast led to increased satiety through increased fullness and PYY concentrations in ‘breakfast skipping’ adolescents. A breakfast rich in dietary protein provides additional benefits through reductions in appetite and energy intake. These findings suggest that the addition of a protein-rich breakfast might be an effective strategy to improve appetite control in young people.

The Effect of Eating Frequency on Appetite Control and Food Intake: Brief Synopsis of Controlled Feeding Studies

Increased eating frequency is postulated to increase metabolism, reduce hunger, improve glucose and insulin control, and reduce body weight, making it an enticing dietary strategy for weight loss and/or the maintenance of a healthy body weight. Because past research has primarily focused on the effects of eating frequency on changes in energy expenditure and body weight, limited data exist surrounding the impact of eating frequency on appetite control and energy intake. We provide a brief review of the controlled-feeding studies that primarily targeted the appetitive, hormonal, and food intake responses potentially altered with eating frequency. The 3 meal/d pattern served as the reference for defining increased or reduced eating frequency. In general, increased eating frequency led to lower peaks (P < 0.05) in perceived appetite, satiety, glucose, insulin, ghrelin, and PYY responses compared with reduced eating frequency. However, when examining these responses over the course of the day (i.e. using area under the curve assessments), no differences in any of these outcomes were observed. The rate of gastric emptying also appears to be unaltered with increased eating frequency. Subsequent food intake was examined in several studies with conflicting results. Regarding the effect of reduced eating frequency, several studies indicate significant increases in perceived appetite and reductions in perceived satiety when 1 or 2 meals were eliminated from the daily diet. Taken together, these findings suggest that increased eating frequency (>3 eating occasions/d) has minimal, if any, impact on appetite control and food intake, whereas reduced eating frequency(<3 eating occasions/d) negatively effects appetite control.

The influence of higher protein intake and greater eating frequency on appetite control in overweight and obese men.

The purpose of this study was to determine the effects of dietary protein intake and eating frequency on perceived appetite, satiety, and hormonal responses in overweight/obese men. Thirteen men (age 51 ± 4 years; BMI 31.3 ± 0.8 kg/m2) consumed eucaloric diets containing normal protein (79 ± 2 g protein/day; 14% of energy intake as protein) or higher protein (138 ± 3 g protein/day; 25% of energy intake as protein) equally divided among three eating occasions (3‐EO; every 4 h) or six eating occasions (6‐EO; every 2 h) on four separate days in randomized order. Hunger, fullness, plasma glucose, and hormonal responses were assessed throughout 11 h. No protein × eating frequency interactions were observed for any of the outcomes. Independent of eating frequency, higher protein led to greater daily fullness (P < 0.05) and peptide YY (PYY) concentrations (P < 0.05). In contrast, higher protein led to greater daily ghrelin concentrations (P < 0.05) vs. normal protein. Protein quantity did not influence daily hunger, glucose, or insulin concentrations. Independent of dietary protein, 6‐EO led to lower daily fullness (P < 0.05) and PYY concentrations (P < 0.05). The 6‐EO also led to lower glucose (P < 0.05) and insulin concentrations (P < 0.05) vs. 3‐EO. Although the hunger‐related perceived sensations and hormonal responses were conflicting, the fullness‐related responses were consistently greater with higher protein intake but lower with increased eating frequency. Collectively, these data suggest that higher protein intake promotes satiety and challenge the concept that increasing the number of eating occasions enhances satiety in overweight and obese men.

Food form and portion size affect postprandial appetite sensations and hormonal responses in healthy, nonobese, older adults.

Data are limited concerning the dietary factors that influence appetite control in older adults. This study examined the effects of food form and portion size on appetite in 43 older adults (age: 72 ± 1 years; BMI: 25.6 ± 0.3 kg/m2). Subjects were assigned to groups based on portion size of the test meal (12.5% (n = 18) vs. 25% (n = 25) of estimated energy need). Subjects randomly consumed, on two separate days, the respective solid or beverage test meal. Appetite sensations and hormonal responses were measured over 4 h. Main effects of food form (P < 0.05) and/or portion size (P < 0.05) were observed for each appetite sensation. Postprandial hunger and desire to eat were greater following beverage vs. solid meal (between 12.5% vs. 25%), whereas fullness was lower after beverage vs. solid meal (P < 0.05). Main effects of food form and/or portion size were observed for glucose, insulin, and ghrelin. Postprandial glucose and insulin concentrations were lower after beverage vs. solid meal (between 12.5% vs. 25%; all comparisons, P < 0.05) whereas beverage meal led to greater 4‐h ghrelin vs. solid meal (P = 0.09). No main effects were observed for glucagon‐like peptide‐1 (GLP‐1) or cholecystokinin (CCK). When adjusting for age, food form remained significant for postprandial hunger and fullness; portion size remained significant for postprandial glucose. Greater hunger and reduced satiety with accompanying glucose, insulin, and ghrelin following the beverage vs. solid meals, and to some extent, in smaller vs. larger portions suggest that appetite control is influenced by food form and portion size in older adults. These findings may enhance the development of appropriate dietary strategies that help to regulate energy balance.

Neuromuscular performance and knee laxity do not change across the menstrual cycle in female athletes

Female athletes incur anterior cruciate ligament ruptures at a rate at least twice that of male athletes. Hypothesized factors for the increased injury risk in females include biomechanical, neuromuscular, and hormonal differences between genders. A wealth of literature exists examining these potential predispositions individually, but the interactions between these factors have not been examined extensively. Our purpose was to investigate changes in neuromuscular control and laxity at the knee across the menstrual cycle of healthy females. Fourteen female collegiate athletes with normal, documented ovulatory menstrual cycles, confirmed ovulation, and no history of serious knee injury participated. The presence and timing of ovulation was determined during a screening cycle with ovulation detection kits and during an experimental cycle with collection of daily urine samples and subsequent analysis of urinary estrone-3-glucuronide (E3G) and pregnanediol-3-glucoronide (PdG), which correlate with circulating estrogen and progesterone. Each subject had measures of knee neuromuscular performance and laxity once during the mid-follicular, ovulatory, and mid-luteal stages of her menstrual cycle. The test battery included assessments of knee flexion and extension peak torque, passive knee joint position sense, and postural control in single leg stance. Knee joint laxity was measured with an arthrometer. Analyses of variance revealed that E3G and PdG levels were significantly different across the three testing sessions, but there were no significant differences in the measures of strength, joint position sense, postural control, or laxity. No significant correlations were found between changes in E3G or PdG levels and changes in the performance and laxity measures between sessions. These results suggest that neuromuscular control and knee joint laxity do not change substantially across the menstrual cycle of females despite varying estrogen and progesterone levels.

Effects of Acute and Chronic Protein Intake on Metabolism, Appetite, and Ghrelin During Weight Loss

Objective: This study evaluated the effects of acute and chronic consumption of higher dietary protein on energy expenditure, macronutrient use, appetite, and appetite‐regulating hormones during weight loss in women.