The interaction between physical activity and nutrition is integral to general health and sports performance

The interaction between physical activity and nutrition is integral to general health and sports performanc

Role of physical activity in regulating appetite and body fat

Recent articles in the press have questioned the role of physical activity in regulating appetite and controlling bodyweight. These articles can be confusing and misleading for the public. Yet this is a complex area and there is disagreement about the importance of physical activity even among academics. Uncertainty and misunderstanding in this area may be related to the heterogeneity of the term ‘physical activity’ which encompasses sporting pursuits with extremely high levels of energy expenditure over prolonged periods of time, as well as everyday tasks involving much lower levels of energy expenditure on an intermittent basis. This latter form of physical activity includes what has been termed ‘non-exercise activity thermogenesis’ (NEAT). In the right circumstances, physical activity can make a major contribution to the maintenance of a healthy weight even in the absence of dietary control although a combination of the two is almost certain to be more effective. In the long-term, evidence suggests that for most people exercise is likely to lead to only modest weight loss. This may be due to an insufficient amount of physical activity being performed together with compensatory changes in eating and exercise behaviours. This is hard to prove because energy intake and energy expenditure are difficult to quantify in free-living situations. Individual differences in the way people respond to exercise due to both environmental (e.g. social class, education level, income, eating and exercise behaviours of family and peers, weather etc.) and genetic factors also contribute to uncertainty about the effectiveness of physical activity for weight control. Nevertheless, physical activity remains a vital component of a healthy lifestyle due to its positive influence on energy balance as well as its potential to reduce the risk of lifestyle-related diseases

Acute exercise increases feeding latency in healthy normal weight young males but does not alter energy intake

This study investigated the acute influence of exercise on eating behaviour in an ecologically valid setting whereby healthy active males were permitted complete ad libitum access to food. Ten healthy males completed two, 8 h trials (exercise and control) in a randomised-crossover design. In the exercise trials participants consumed a breakfast snack and then rested for 1 h before undertaking a 60 min run (72% of V˙O2 max) on a treadmill. Participants then rested in the laboratory for 6 h during which time they were permitted complete ad libitum access to a buffet meal. The timing of meals, energy/macronutrient intake and eating frequency were assessed. Identical procedures were completed in the control trial except no exercise was performed. Exercise increased the length of time (35 min) before participants voluntarily requested to eat afterwards. Despite this, energy intake at the first meal consumed, or at subsequent eating episodes, was not influenced by exercise (total trial energy intake: control 7426 kJ, exercise 7418 kJ). Neither was there any difference in macronutrient intake or meal frequency between trials. These results confirm that food intake remains unaffected by exercise in the immediate hours after but suggest that exercise may invoke a delay before food is desired

An update on accumulating exercise and postprandial lipaemia: translating theory into practice

Over the last two decades, significant research attention has been given to the acute effect of a single bout of exercise on postprandial lipaemia. A large body of evidence supports the notion that an acute bout of aerobic exercise can reduce postprandial triacylglycerol (TAG) concentrations. However, this effect is short-lived emphasising the important role of regular physical activity for lowering TAG concentrations through an active lifestyle. In 1995, the concept of accumulating physical activity was introduced in expert recommendations with the advice that activity can be performed in several short bouts throughout the day with a minimum duration of 10 minutes per activity bout. Although the concept of accumulation has been widely publicised, there is still limited scientific evidence to support it but several studies have investigated the effects of accumulated activity on health-related outcomes to support the recommendations in physical activity guidelines. One area, which is the focus of this review, is the effect of accumulating exercise on postprandial lipaemia. We propose that accumulating exercise will provide additional physical activity options for lowering postprandial TAG concentrations relevant to individuals with limited time or exercise capacity to engage in more structured forms of exercise, or longer bouts of physical activity. The benefits of accumulated physical activity might translate to a reduced risk of cardiovascular disease in the long-term. Copyright © 2013 The Korean Society for Preventive Medicine

High intensity interval exercise and postprandial triacylglycerol

This review examined if high intensity interval exercise (HIIE) reduces postprandial triacylglycerol (TAG) concentrations. Fifteen studies were identified, in which the effect of interval exercise conducted at an intensity of >65% of maximal oxygen uptake was evaluated on postprandial TAG concentrations. Analysis was divided between studies which included supramaximal exercise and those which included submaximal interval exercise. Ten studies examined the effect of a single session of low-volume HIIE including supramaximal sprints on postprandial TAG. Seven of these studies noted reductions in postprandial total TAG area under the curve the morning after exercise of between ~10%-21% compared with rest but three investigations found no significant difference in TAG concentrations. Variations in the HIIE protocol used, inter-individual variation or insufficient time post-exercise for an increase in lipoprotein lipase activity are proposed reasons for the divergent results among studies. Five studies examined the effect of high-volume submaximal interval exercise on postprandial TAG. Four of these studies were characterised by high exercise energy expenditure and effectively attenuated total postprandial TAG concentrations by ~15%-30% but one study with a lower energy expenditure found no effect on TAG. The evidence suggests that supramaximal HIIE can induce large reductions in postprandial TAG concentrations but findings are inconsistent. Submaximal interval exercise offers no TAG metabolic or time advantage over continuous aerobic exercise but could be appealing in nature to some individuals. Future research should examine if submaximal interval exercise can reduce TAG concentrations in line with more realistic and achievable exercise durations of 30 minutes per day

Influence of brisk walking on appetite, energy intake, and plasma acylated ghrelin

Purpose: This study examined the effect of an acute bout of brisk walking on appetite, energy intake, and the appetite-stimulating hormone-acylated ghrelin. Methods: Fourteen healthy young males (age 21.9 +/- 0.5 yr, body mass index 23.4 +/- 0.6 kg.m(-2), (V) over dotO(2max) 55.9 +/- 1.8 mL.kg(-1).min(-1); mean +/- SEM) completed two 8-h trials (brisk walking and control) in a randomized counterbalanced fashion. The brisk walking trial commenced with 60 min of subjectively paced brisk walking on a level-motorized treadmill after which participants rested for 7 h. Participants rested for the duration of the control trial. Ad libitum buffet meals were offered twice during main trials (1.5-2 and 5-5.5 h). Appetite (hunger, fullness, satisfaction, and prospective food consumption) was assessed at 30-min intervals throughout. Levels of acylated ghrelin, glucose, insulin, and triacylglycerol were determined from plasma. Results: Sixty minutes of brisk walking (7.0 +/- 0.1 km.h(-1)) yielded a net (exercise minus resting) energy expenditure of 2008 +/- 134 kJ, yet it did not significantly influence appetite, energy/macronutrient intake, or the plasma concentration of acylated ghrelin either during or after exercise (P > 0.05). Participants did not compensate for energy expended during walking, therefore a deficit in energy was induced (1836 kJ, 439 kcal) relative to control. Conclusions: This study demonstrates that, despite inducing a moderate energy deficit, an acute bout of subjectively paced brisk walking does not elicit compensatory responses in acylated ghrelin, appetite, or energy intake. This finding lends support for a role of brisk walking in weight management

The association between leisure-time physical activity, low HDL-cholesterol and mortality in a pooled analysis of nine population-based cohorts

The objective of this study was to investigate associations between leisure-time physical activity, low high-density lipoprotein cholesterol (HDL-C) and mortality. Self-reported leisure-time physical activity, HDL-C concentration, and mortality were assessed in 37,059 adults in Health Survey for England and Scottish Health Survey. Meeting physical activity guidelines was defined as ≥150 min wk−1 of moderate-intensity activity, ≥75 min wk−1 of vigorous-intensity activity, or equivalent combinations. Low HDL-C was defined as <1.03 mmol L−1. Cox proportional hazard models were adjusted for age, sex, smoking, total cholesterol, systolic blood pressure, body mass index, longstanding illness, and socioeconomic status. There were 2250 deaths during 326,016 person-years of follow-up. Compared with those who met physical activity guidelines and whose HDL-C was normal (reference group), all-cause mortality risk was not elevated in those who met physical activity guidelines and whose HDL-C concentration was low (hazard ratio: 1.07; 95% confidence interval: 0.75, 1.53). Compared with the reference group, all-cause mortality risk was elevated in those who did not meet physical activity guidelines and whose HDL-C was normal (1.37; 1.16, 1.61), and in those who did not meet physical activity guidelines and whose HDL-C was low (1.65; 1.37, 1.98). Cardiovascular disease mortality hazard ratios were similar, although confidence intervals were wider. There was no statistically significant evidence of biological interaction between physical inactivity and low HDL-C. This novel study supports the notion that leisure-time physical activity be recommended in those with low HDL-C concentration who may be resistant to the HDL-raising effect of exercise training

The importance of vigorous-intensity, leisure-time physical activity in reducing cardiovascular disease mortality risk in the obese

Objective: To investigate the role of vigorous-intensity leisure-time physical activity in reducing cardiovascular disease (CVD) mortality risk in the obese. Methods: Trained interviewers assessed physical activity and body mass index (BMI) in 59,005 adult participants (57±12 years of age [mean±SD]; 46.5% male) in the household based surveillance studies, Health Survey for England and Scottish Health Survey. Mortality was ascertained from death certificates. Data were collected from January 1994 to March 2011. Cox proportional hazards models were adjusted for age, sex, smoking habit, total physical activity, longstanding illness, prevalent CVD, and occupation. Results: There were 2,302 CVD deaths during 532,251 person-years of follow-up (9±4 years). Some 25% of participants were categorized as obese (BMI ≥30 kg·m-236 ). Leisure-time physical activity was inversely associated and BMI was positively associated with CVD mortality. Compared to those who reported meeting physical activity guidelines, including some vigorous-intensity physical activity, and who had a normal BMI (18.5-24.9 kg·m-239 ) (reference group), CVD mortality hazard ratio was not significantly different in the obese who also reported meeting physical activity guidelines, including some vigorous-intensity physical activities (1.25; 95% confidence interval: 0.50, 3.12). Compared to the reference group, CVD mortality hazard ratio was more than twofold in the obese who reported meeting physical activity guidelines, including only moderate-intensity physical activities (2.52; 95% CI: 1.15, 2.53). Conclusion: This large, statistically powerful study suggests that vigorous-intensity leisure time physical activity is important in reducing CVD mortality risk in the obese

Exercise and coronary heart disease risk markers in South Asian and European men

PURPOSE: South Asians have a higher than average risk of coronary heart disease. The reasons for this are unclear but physical inactivity and/or poor responsiveness to exercise may play a role. This study compared the effect of prior exercise on postprandial triacylglycerol (TAG), glucose, insulin, interleukin-6 (IL-6) and soluble intercellular adhesion molecule-1 (sICAM-1) concentrations in South Asian and European men. METHODS: Ten healthy South Asian men (i.e. nine Indian men and one Pakistani man) and 10 healthy European men aged 20 to 28 years completed two, 2-day trials (exercise and control) in a randomised-crossover design. On the afternoon of day 1 of the exercise trial, participants ran on a treadmill for 60 minutes at approximately 70% of maximal oxygen uptake. Participants rested on day 1 of the control trial. On day 2 of both trials participants rested and consumed high fat (57% of energy content) test meals for breakfast (0 h) and lunch (4 h). Fourteen venous blood samples were collected from a cannula between 0 h and 9 h for metabolic measurements. RESULTS: Three-way ANOVA identified higher (P < 0.05) postprandial TAG and insulin concentrations in South Asian versus European men. Exercise lowered postprandial TAG and IL-6 and elevated sICAM-1 concentrations. An interaction effect indicated a greater decrease (22 versus 10%) in TAG area under the concentration versus time curve after exercise in South Asian than European men. CONCLUSIONS: Postprandial TAG and insulin responses to high fat meals were elevated in these South Asian men but acute exercise was equally if not more effective for reducing postprandial lipemia in South Asian than in European men

Influence of prolonged treadmill running on appetite, energy intake and circulating concentrations of acylated ghrelin

The effects of prolonged treadmill running on appetite, energy intake and acylated ghrelin (an appetite stimulating hormone) were examined in 9 healthy males over the course of 24 h. Participants completed 2 experimental trials (exercise and control) in a randomised - crossover fashion. In the exercise trial participants ran for 90 min at 68.8 ± 0.8% of maximum oxygen uptake followed by 8.5 h of rest. Participants returned to the laboratory on the following morning to provide a fasting blood sample and ratings of appetite (24 h measurement). No exercise was performed on the control trial. Appetite was measured within the laboratory using visual analogue scales and energy intake was assessed from ad libitum buffet meals. Acylated ghrelin was determined from plasma using an ELISA assay. Exercise transiently suppressed appetite and acylated ghrelin but each remained no different from control values in the hours afterwards. Furthermore, despite participants expending 5324 kJ during exercise there was no compensatory increase in energy intake (24 h energy intake; control 17191 kJ, exercise 17606 kJ). These findings suggest that large energy deficits induced by exercise do not lead to acute compensatory responses in appetite, energy intake or acylated ghrelin