A decrease in physical activity affects appetite, energy, and nutrient balance in lean men feeding ad libitum

BACKGROUND: It is not clear how decreased activity quantitatively affects energy balance (EB) in subjects feeding ad libitum. OBJECTIVE: We assessed the effect of an imposed sedentary routine on appetite, energy intake (EI), EB, and nutrient balance in lean men for 7 d. DESIGN: Six men with a mean (+/-SD) age of 23.0 +/- 2.3 y, weight of 69.2 +/- 11.4 kg, and height of 1.76 +/- 0.07 m were each studied twice during a sedentary [1.4 x resting metabolic rate (RMR)] and a moderately active (1.8 x RMR) regimen. During each treatment, they resided in the whole-body indirect calorimeter for the 7 d and had ad libitum access to a medium-fat diet of constant, measurable composition. Meal size, frequency, and composition were continually monitored. Motivation to eat was recorded during waking hours. Subjects were weighed in light clothing each morning, and their weight was corrected to nude. RESULTS: Energy expenditure was 9.7 and 12.8 MJ/d [P < 0.01; SE of the difference between means (SED) = 0.41] during the sedentary and active regimens, respectively. EI was 13.5 and 14.4 MJ/d (P = 0.463, SED = 1.06), respectively. There was no regimen effect on hunger, appetite, or body weight. By day 7, cumulative EB was 26.3 and 11.1 MJ, respectively. CONCLUSIONS: Reducing a level of physical activity from 1.8 to 1.4 x RMR can markedly affect EB. A sedentary routine does not induce a compensatory reduction of EI and leads to a significantly positive EB, most of which is stored as fat.     

Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum

BACKGROUND: Altering the macronutrient composition of the diet influences hunger and satiety. Studies have compared high- and low-protein diets, but there are few data on carbohydrate content and ketosis on motivation to eat and ad libitum intake. OBJECTIVE: We aimed to compare the hunger, appetite, and weight-loss responses to a high-protein, low-carbohydrate [(LC) ketogenic] and those to a high-protein, medium-carbohydrate [(MC) nonketogenic] diet in obese men feeding ad libitum. DESIGN: Seventeen obese men were studied in a residential trial; food was provided daily. Subjects were offered 2 high-protein (30% of energy) ad libitum diets, each for a 4-wk period-an LC (4% carbohydrate) ketogenic diet and an MC (35% carbohydrate) diet-randomized in a crossover design. Body weight was measured daily, and ketosis was monitored by analysis of plasma and urine samples. Hunger was assessed by using a computerized visual analogue system. RESULTS: Ad libitum energy intakes were lower with the LC diet than with the MC diet [P=0.02; SE of the difference (SED): 0.27] at 7.25 and 7.95 MJ/d, respectively. Over the 4-wk period, hunger was significantly lower (P=0.014; SED: 1.76) and weight loss was significantly greater (P=0.006; SED: 0.62) with the LC diet (6.34 kg) than with the MC diet (4.35 kg). The LC diet induced ketosis with mean 3-hydroxybutyrate concentrations of 1.52 mmol/L in plasma (P=0.036 from baseline; SED: 0.62) and 2.99 mmol/L in urine (P<0.001 from baseline; SED: 0.36). CONCLUSION: In the short term, high-protein, low-carbohydrate ketogenic diets reduce hunger and lower food intake significantly more than do high-protein, medium-carbohydrate nonketogenic diets.     

Nutrient balance and energy expenditure during ad libitum feeding of high-fat and high-carbohydrate diets in humans.

To study the influence of diet composition on regulation of body weight, we fed 21 weight-stable subjects (11 lean, 10 obese) high-carbohydrate (HC) and high-fat (HF) diets for 1 wk each. Although diet composition was fixed, total energy intake was unrestricted. Subjects had a higher energy intake on the HF (11,039 +/- 2700 kJ/d) than on the HC (10,672 +/- 2617 kJ/d) diet (P less than 0.05), but energy expenditure was not different between diets. On day 7 of the HC diet, carbohydrate (CHO) oxidation was significantly related to CHO intake with the slope of the regression line 0.99, suggesting that overall CHO balance was near zero. However, the slope of the regression line was greater for obese than for lean subjects. On day 7 of the HF diet, fat oxidation was significantly related to fat intake but the slope of the line was 0.50, suggesting that overall fat balance was positive. However, this relationship was due entirely to lean subjects, with obese subjects showing no relationship between fat intake and oxidation.     

Effects of exercise and restrained eating behaviour on appetite control

Obesity is a global epidemic; increased consumption of energy-dense food and reduced physical activity levels are likely to be the main drivers. Previous cross-sectional research has shown that sedentary males, unlike their active counterparts, are unable to compensate for previous energy intake (EI). Using a longitudinal design a 6-week exercise intervention was found to improve short-term appetite control, leading to a more 'sensitive' eating behaviour in response to previous EI, both acutely at a test meal and for the next 24 h. Although the mechanisms whereby acute and chronic exercise improves short-term appetite remain unknown, post-ingestive satiety peptides are likely to be involved. Acute exercise was found to increase postprandial levels of polypeptide YY, glucagon-like peptide-1 and pancreatic polypeptide but to have no impact on ghrelin, suggesting that exercise can trigger physiological changes in satiety hormone secretion that could help in appetite control and weight maintenance. In the context of an increased availability of highly-palatable food, dietary restraint may be increasingly important. Although restraint has been associated with abnormal eating behaviour, in the laboratory no counter-regulation was found in restrained eaters when presented with a buffet meal 60 min after a high-energy preload or when a pasta-meal was presented 3 h after preloading. Although restraint was not found to impact on polypeptide YY or TAG, lower postprandial glucose and insulin plasma levels were observed in restrained eaters, together with increased feelings of fullness. In conclusion, short-term appetite control seems to be favourably modified by exercise, while the impact of restraint on appetite seems to be more complex.     

Greater appetite control associated with an increased frequency of eating in lean males

Eight healthy males of age 22.9+/-4.2 years (mean+/-SD) and body weight 73.26+/-11.50 kg, with BMI of 23.11+/-2.84 kg/m(2)underwent two different eating meal frequency patterns on 2 separate days. On both days they were fed approximately 33.3% of their average daily energy requirements as a breakfast pre-load meal: served either as a single meal (SINGLE) or divided into five equal portions (served hourly) (MULTI). Five and a half hours after the initial meal, an ad libitum meal was served. Venous blood was tested to determine plasma glucose and serum insulin concentrations every hour until the ad libitum lunch, and at 15-, 45- and 75-min after lunch. Visual analogue scales (VAS) were completed every hour until the ad libitum lunch, and at 15-, 45- and 75-min after lunch as a measure to determine hunger, appetite and satiety indices. Although both groups were fed isocaloric and identical macronutrient "breakfast pre-loads" (3450+/-466 kJ), the SINGLE group consumed 26.6% more (p<0.02) energy in the ad libitum lunch (5111+/-1502 kJ vs. 3752+/-893 kJ) than the MULTI group did. The pre-load feeding pattern had no effect on blood glucose responses throughout the trial. Following the larger SINGLE pre-load, serum insulin concentration rose to a higher (p<0.01) level compared to the first of the MULTI pre-load meals (123.04+/-61.51 microIU/ml vs. 37. 30+/-26.65 microIU/ml SINGLE vs. MULTI, respectively). Serum insulin rose to a higher (p<0.01) level following the fifth and final of the MULTI pre-load meals compared to the serum insulin levels in the SINGLE group at the same time into the trial (74. 21+/-51.64 microIU/ml vs. 24.98+/-13.46 microIU/ml MULTI vs. SINGLE, respectively). Despite consuming more energy in the ad libitum lunch, the SINGLE group showed no difference in serum insulin concentration following the ad libitum lunch compared to the insulin response of the MULTI group. These data suggest that when the nutrient load was spread into equal amounts and consumed evenly through the day in lean healthy males, there was an enhanced control of appetite. This greater control of satiety when consuming smaller multiple meals may possibly be linked to an attenuation in insulin response although clearly both other physical (gastric stretch) and physiological (release of gastric hormones) factors may also be affected by the periodicity of eating.     

The effect of exercise on food intake in men and women

To study the effect of acute exercise on caloric intake in normal-weight young people, food intake was monitored in 10 men and 10 women during consecutive 5-d periods, one with and one without exercise. Food intake during the exercise period was compared with that during the control period. Caloric intake during the control period was 2467 +/- 165 kcal/d (means +/- SEM) for men and 1831 +/- 103 kcal/d for women. During the exercise period the men increased their caloric intake to 2658 +/- 188 kcal/d and the women's caloric intake remained unchanged, 1830 +/- 91 kcal/d. Caloric intake was not affected by sequence of treatment or duration of protocol. Men responded to 5 d of acute exercise with increased caloric intake (208 +/- 64 kcal/d), which was insufficient to compensate for the caloric cost of exercise (596 kcal/d above resting metabolic rate). Women did not change their caloric intake despite expending 382 kcals/d during exercise. Consequently, both normal-weight men and women were in negative caloric balance during the exercise period.     

Short-term isocaloric manipulation of carbohydrate intake: effect on subsequent ad libitum energy intake

Background  

Isocaloric manipulation of carbohydrate or fat intake could alter subsequent ad libitum food intake.     

The effect of exercise on water balance in premenopausal physically active women

OBJECTIVE: This controlled feeding study examined the effects of exercise on daily water intake (particularly ad libitum water intake), water output, whole-body water balance, and hydration status in physically active, premenopausal women. DESIGN: The randomized crossover design consisted of three 8-day trials: placebo and no exercise, placebo and exercise (1-hour cycling bout per day at 65%-70% of heart rate reserve), and 800 mg calcium supplementation and exercise. During each trial, controlled quantities of the same foods and beverages were provided and ad libitum water intake was quantified. Water input included measured water from foods and beverages, measured ad libitum intake, and estimated metabolic production. Water output included measured losses in urine and stool, and estimated insensible losses from respiration and non-sweating perspiration (insensible diffusion through the skin). SUBJECTS: Participants were 26 women, age 25+/-5 years, body mass index 22+/-2, and VO(2peak) 43+/-6 mLxkg(-1)xmin(-1) (mean+/-standard deviation). RESULTS: Ad libitum water intake was 363 g/day more (P<0.05) for the placebo and exercise (1,940+/-654 g/day) and calcium supplementation and exercise (1,935+/-668 g/day) trials, compared with placebo and no exercise trial (1,575+/-667 g/day), and total water input was correspondingly higher in placebo and exercise and calcium supplementation and exercise trials compared with the placebo and no exercise trial. Urine, stool, and total water outputs were not different among trials. Apparent net water balance (representative of sweat water output) was 367 g/day more (P<0.05) in placebo and exercise (679+/-427 g/day) and calcium supplementation and exercise (641+/-519 g/day) trials compared with placebo and no exercise trial (293+/-419 g/day). Hydration status was clinically normal during all three trials. Calcium supplementation did not influence water balance. CONCLUSION: These results support that young, physically active women can completely compensate for exercise-induced sweat losses by increasing ad libitum water intake, and not decreasing non-sweat water outputs or impairing hydration status.     

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.     

Moderate exercise, postprandial energy expenditure, and substrate use in varying meals in lean and obese men

Maximizing postprandial energy expenditure and fat oxidation could be of clinical relevance for the treatment of obesity. This study investigated the effect of prior exercise on energy expenditure and substrate utilization after meals containing varying amounts of macronutrients. Eight lean (11.6%+/-4.0% body fat, M+/-SD) and 12 obese (35.9%+/-5.3% body fat) men were randomly assigned to a protein (43% protein, 30% carbohydrate) or a carbohydrate (10% protein, 63% carbohydrate) meal. The metabolic responses to the meals were investigated during 2 trials, when meals were ingested after a resting period (D) or cycling exercise (Ex+D; 65% of oxygen consumption reserve, 200 kcal). Energy expenditure, substrate utilization, and glucose and insulin responses were measured for 4 hr during the postprandial phase. Although postprandial energy expenditure was not affected by prior exercise, the total amount of fat oxidized was higher during Ex+D than during D (170.8+/-60.1 g vs. 137.8+/-50.8 g, p< .05), and, accordingly, the use of carbohydrate as substrate was decreased (136.4+/-45.2 g vs. 164.0+/-42.9 g, p< .05).After the protein meal fat-oxidation rates were higher than after carbohydrate intake (p< .05), an effect independent of prior exercise. Plasma insulin tended to be lower during Ex+D (p= .072) and after the protein meal (p= .066). No statistically significant change in postprandial blood glucose was induced by prior exercise. Exercising before meal consumption can result in a marked increase in fat oxidation, which is independent of the type of meal consumed.     

Effects of disordered eating and obesity on weight, craving, and food intake during ad libitum smoking and abstinence

Although there is empirical support for the association between smoking, disordered eating, and subsequent weight gain upon smoking cessation, there have been no prospective studies to track changes in eating patterns during smoking abstinence and explore underlying biobehavioral processes. To help fill these gaps, we recruited four groups of women (N=48, 12/group) based on presence vs. absence of obesity and on low vs. high risk of severe dieting and/or binge-eating to participate in a laboratory study of eating in the context of ad libitum smoking and smoking abstinence. Participants [mean age 31.3 years; Fagerstrom Test of Nicotine Dependence (FTND) 4.3; smoking rate 18.7 cigarettes/day] completed two sessions: one after ad libitum smoking, the other after 2 days' smoking abstinence, in counterbalanced order. After a half-day's restricted eating, participants watched a video, with measured amounts of preselected preferred food available throughout. Cigarettes were available during the ad libitum smoking session. High-risk women weighed more after 2 days' abstinence than during the ad libitum smoking condition, whereas low-risk women did not differ across conditions. Nicotine craving changed significantly more in anticipation of nicotine deprivation for high-BMI women than their low-BMI counterparts. Caloric intake was marginally attenuated during abstinence for low-BMI compared with high-BMI participants (P<.10), an effect primarily accounted for by differences in protein intake (P<.10). These findings suggest that low-BMI women may be less prone to weight gain during early abstinence, possibly because they compensate for metabolic changes induced by nicotine washout by eating less. Craving increases experienced by high-BMI women during abstinence under conditions of food deprivation may contribute to difficulty quitting in these women.     

The effect of low-carbohydrate diet on the pattern of hormonal changes during incremental, graded exercise in young men

The purpose of this study was to discover whether severe dietary carbohydrate (CHO) restriction modifies the relationship between exercise intensity and hormonal responses to exercise. Changes in the plasma adrenaline (A), noradrenaline (NA), growth hormone (hGH), testosterone (T), and blood lactate (LA) during an incremental exercise performed until volitional exhaustion were determined in 8 physically active volunteers after 3 days on low CHO (< 5% of energy content; L-CHO) and isocaloric mixed (M) diets. Following L-CHO diet, the basal plasma A, NA, and hGH concentrations were increased, whilst T and LA levels were decreased. During exercise all the hormones increased exponentially, with thresholds close to that of LA. Neither the magnitude nor the pattern of the hormonal changes were affected by L-CHO diet except the NA threshold, which was lowered. Blood LA response to exercise was diminished and LA threshold was shifted towards higher loads by L-CHO diet. It is concluded that restriction of CHO intake (a) does not affect the pattern of changes in plasma A, hGH, and T concentrations during graded exercise but lowers NA threshold, indicating increased sensitivity of the sympathetic nervous system to exercise stimulus; (b) alters the basal and exercise levels of circulating hormones, which may have an impact on the balance between anabolic and catabolic processes and subsequently influence the effectiveness of training.     

Role of protein and carbohydrate sources on acute appetite responses in lean and overweight men

Dietary protein induces greater satiety compared with carbohydrate in lean subjects, which may involve appetite-regulatory gut hormones. Little is known about the duration of effect, influence of protein and carbohydrate source and relevance to non-lean individuals. We compared the effect of various dietary proteins and carbohydrates on post-prandial appetite ratings, ad libitum energy intake (EI) and appetite hormones in lean and overweight men. Three randomised double-blinded cross-over studies examined appetite response (appetite ratings, ghrelin, glucagon-like peptide-1 (GLP-1) and cholecystokinin) to liquid preloads over three to four hours followed by a buffet meal to assess ad libitum EI. The 1-MJ preloads contained ∼55 g of protein (whey, casein, soy and gluten), carbohydrate (glucose, lactose and fructose) or combined whey/fructose. EI was 10% higher following glucose preloads compared with protein preloads, observed at three hours but not four hours. Protein ingestion was followed by prolonged elevation of cholecystokinin and GLP-1 (two hours) and suppression of ghrelin (three to four hours) compared with glucose and independent of protein type. Replacing some whey with fructose attenuated the effect of protein on these hormones. Treatment effects on EI and appetite hormones were independent of bodyweight status, despite higher GLP-1 and lower ghrelin in overweight subjects. Protein-rich liquid preloads reduce EI over three hours in overweight men compared with glucose. These findings suggest a potential application for protein-rich drinks and/or foods to facilitate reduced EI. Future studies should explore additional dietary manipulations that may enhance this relationship, and confirm these effects within the context of energy-restricted dietary patterns.     

Whole-body fat oxidation rate and plasma triacylglycerol concentrations in men consuming an ad libitum high-carbohydrate or low-carbohydrate diet

BACKGROUND: High-carbohydrate diets may increase plasma triacylglycerol concentrations either by increasing production of triacylglycerols or by reducing their clearance. OBJECTIVE: We assessed whether the changes in plasma triacylglycerol concentrations induced by dietary interventions were associated with the changes in whole-body fat oxidation rates. DESIGN: In a parallel study, 37 healthy male subjects [body mass index (in kg/m(2)): 28 +/- 5, age: 34 +/- 11 y (x +/- SD)] consumed an ad libitum high-carbohydrate (60% of energy; n = 19) or low-carbohydrate (46% of energy), high-fat (41% of energy, 23% as monounsaturated fatty acids; n = 18) diet for 7 wk. The following variables were measured before and after the dietary interventions: 1) plasma triacylglycerols before and 2, 4, 6, and 8 h after a meal (containing 40% of daily energy needs and 41% fat); 2) indirect calorimetry throughout the 8-h test; and 3) postheparin plasma lipoprotein lipase (phLPL) activity at time 8 h of the test. RESULTS: The diets induced changes in 1) body weight: -2.5 +/- 2.8 kg (P < 0.01) and -1.7 +/- 3.1 kg (P < 0.05) and 2) fasting plasma triacylglycerols: 0.0 +/- 0.4 mmol/L (NS) and -0.3 +/- 0.3 mmol/L (P < 0.05) for the high-carbohydrate and the low-carbohydrate diets, respectively. In normoinsulinemic subjects (fasting insulin < 100 pmol/L), dietary changes in postprandial triacylglycerols were significantly predicted by changes in phLPL, body weight, respiratory quotient (or fat oxidation), and the type of diet (stepwise multiple linear regression). CONCLUSION: Postprandial plasma triacylglycerol concentrations may depend at least partly on fat oxidation, body weight, and LPL activity.     

Effects of exercise intensity on food intake and appetite in women

BACKGROUND: Increasing exercise intensity has been shown to reduce energy intake in men. OBJECTIVE: The main objective of this study was to investigate the effects of exercise intensity on energy intake in women. DESIGN: Thirteen moderately active (peak oxygen uptake: 44.0 +/- 4.7 mL . kg(-1) . min(-1)) women [body mass index (in kg/m(2)): 22.2 +/- 2.4; age: 22.2 +/- 2.0 y] were subjected to 3 experimental conditions: control with no exercise and 2 equicaloric (350 kcal) low- (LIE) and high- (HIE) intensity exercise sessions at 40% and 70% of peak oxygen uptake, respectively. After each session, the participants ate ad libitum from buffet-type meals at lunch and dinner and ate snacks during the afternoon and evening. Visual analogue scales were used to rate appetite. RESULTS: More energy was ingested at lunchtime after the HIE session than after the control session (878 +/- 309 and 751 +/- 230 kcal, respectively; P = 0.02). Relative energy intake (postexercise energy intake corrected for the energy cost of exercise above the resting level) at lunch was lower after the LIE session than after the control session (530 +/- 233 and 751 +/- 230 kcal, respectively; P < 0.001) and was lower after the HIE session than after the control session (565 +/- 301 and 751 +/- 230 kcal, respectively; P < 0.01). Similarly, daily energy intake tended to increase during the HIE session relative to that during the control session. No treatment effect was found for appetite scores throughout the experiment. CONCLUSION: The results suggest that HIE increases energy intake in women.     

Diet composition, energy intake, and exercise in relation to body fat in men and women

This study examined the relationships among body fat, diet composition, energy intake, and exercise in adults. Male (n = 107) and female (n = 109) adults aged 18-71 y (36.6 +/- 1.0 y, means +/- SEM) were hydrostatically weighed to determine body fat (5.7-49.0% of total weight). Diet and exercise behaviors were determined by use of a questionnaire. As body fat increased, percent of energy intake derived from fat increased (p less than 0.001) whereas the percent from carbohydrate decreased (p less than 0.001). There was no relationship between energy intake and adiposity although leanness and exercise were related (p less than 0.001). When subgroups of lean and obese subjects were compared, the lean subjects derived approximately 29% of their energy from fat and 53% from carbohydrate vs 35% and 46%, respectively, for the obese subjects. No differences were found between groups for energy intake but the lean individuals exercised more often than did the obese individuals. These data suggest that diet composition may play as important a role in fat deposition as do energy intake and lack of exercise.