The effect of inactivity on dietary intake and energy homeostasis

Impact of sedentarism due to the COVID-19 home confinement on neuromuscular, cardiovascular and metabolic health: Physiological and pathophysiological implications and recommendations for physical and nutritional countermeasures

The COVID-19 pandemic is an unprecedented health crisis as entire populations have been asked to self-isolate and live in home-confinement for several weeks to months, which in itself represents a physiological challenge with significant health risks. This paper describes the impact of sedentarism on the human body at the level of the muscular, cardiovascular, metabolic, endocrine and nervous systems and is based on evidence from several models of inactivity, including bed rest, unilateral limb suspension, and step-reduction. Data form these studies show that muscle wasting occurs rapidly, being detectable within two days of inactivity. This loss of muscle mass is associated with fibre denervation, neuromuscular junction damage and upregulation of protein breakdown, but is mostly explained by the suppression of muscle protein synthesis. Inactivity also affects glucose homeostasis as just few days of step reduction or bed rest, reduce insulin sensitivity, principally in muscle. Additionally, aerobic capacity is impaired at all levels of the O₂ cascade, from the cardiovascular system, including peripheral circulation, to skeletal muscle oxidative function. Positive energy balance during physical inactivity is associated with fat deposition, associated with systemic inflammation and activation of antioxidant defences, exacerbating muscle loss. Importantly, these deleterious effects of inactivity can be diminished by routine exercise practice, but the exercise dose-response relationship is currently unknown. Nevertheless, low to medium-intensity high volume resistive exercise, easily implementable in home-settings, will have positive effects, particularly if combined with a 15-25% reduction in daily energy intake. This combined regimen seems ideal for preserving neuromuscular, metabolic and cardiovascular health.

Aging is associated with myocardial insulin resistance and mitochondrial dysfunction

Aging is associated with insulin resistance, often attributable to obesity and inactivity. Recent evidence suggests that skeletal muscle insulin resistance in aging is associated with mitochondrial alterations. Whether this is true of the senescent myocardium is unknown. Twelve young (Y, 4 years old) and 12 old (O, 11 years old) dogs, matched for body mass, were instrumented with left-ventricular pressure gauges, aortic and coronary sinus catheters, and flow probes on left circumflex artery. Before surgery, all dogs participated in a 6-wk exercise program. Dogs underwent measurements of hemodynamics and plasma substrates before and during a 2-h hyperinsulinemic-euglycemic clamp to measure whole body and myocardial glucose and nonesterified fatty acid uptake. Following the protocol, myocardial and skeletal samples were obtained to measure components of the insulin-signaling cascade and mitochondrial structure. There was no difference in plasma glucose (Y, 90 +/- 4 mg/dl; O, 87 +/- 4 mg/dl), but old dogs had higher (P < 0.02) nonesterified fatty acids (Y, 384 +/- 48 micromol/l; O, 952 +/- 97 micromol/l) and plasma insulin (Y, 39 +/- 11 pmol/l; O, 108 +/- 18 pmol/l). Old dogs had impaired total body glucose disposition (Y, 11.5 +/- 1 mg x kg(-1) x min(-1); O, 8.0 +/- 0.5 mg x kg(-1) x min(-1); P < 0.05) and insulin-stimulated myocardial glucose uptake (Y, 3.5 +/- 0.3 mg x min(-1) x g(-1); O, 1.8 +/- 0.3 mg x min(-1) x g(-1); P < 0.05). The impaired insulin action was associated with altered insulin signaling and glucose transporter (GLUT4) translocation. There were myocardial mitochondrial structural changes observed in association with decreased expression of uncoupling protein-3. Aging is associated with both whole body and myocardial insulin resistance, independent of obesity and inactivity, but involving altered mitochondrial structure and impaired cellular insulin action.

Calorie restriction accelerates the catabolism of lean body mass during 2 wk of bed rest

BACKGROUND

Muscle inactivity and low energy intake commonly occur in persons with acute or chronic disease, in astronauts during space flight, and during aging.

OBJECTIVE

We used a crossover design to investigate the effects of the interactions of inactivity and calorie restriction on whole-body composition and protein kinetic regulation in 9 healthy volunteers.

DESIGN

Lean body mass (LBM) was measured by using dual-energy X-ray absorptionmetry before and at the end of 14-d periods of bed rest (B) and controlled ambulation (A) in patients receiving eucaloric (E) or hypocaloric (H) (approximately 80% of total energy expenditure) diets. Whole-body leucine kinetics were determined at the end of the 4 study periods by using a standard stable-isotope technique in the postabsorptive state and during a 3-h infusion of a 0.13 g x kg LBM(-1) x h(-1) amino acid mixture.

RESULTS

In the postabsorptive state, we found a significant (P = 0.04) bed rest x hypocaloric diet interaction for the rate of leucine oxidation, an index of net protein catabolism (A+E: 0.23 +/- 0.01; B+E: 25 +/- 0.01; A+H: 0.23 +/- 0.01; B+H: 0.28 +/- 0.01 micromol x min(-1) x kg LBM(-1)). Bed rest significantly (P < 0.01) decreased amino acid-mediated stimulation of nonoxidative leucine disappearance, an index of protein synthesis (A+E: 35 +/- 2%; B+E: 30 +/- 2%; A+H: 41 +/- 3%; B+H: 32 +/- 2%). B+H decreased LBM by 1.10 +/- 0.1 kg, which is significantly (P < 0.01) greater than the decrease seen with A+E, A+H, or B+E.

CONCLUSION

Calorie restriction enhanced the catabolic response to inactivity by combining greater protein catabolism in the postabsorptive state with an impaired postprandial anabolic utilization of free amino acids.

Energy Requirements in Hospitalized Elderly People

OBJECTIVES

To estimate energy intake and energy expenditure (EE) in elderly hospitalized patients recovering from an acute illness.

DESIGN

Cross-sectional evaluation of the disparity between energy intake and expenditure.

PARTICIPANTS

Ninety geriatric patients (mean age+/-standard deviation 79.7+/-7.5) admitted to acute care or rehabilitation units.

MEASUREMENTS

Patients' energy intake and resting EE (REE) were measured over a 3-day period. Blood samples were taken to determine C-reactive protein (CRP), creatinine, and albumin concentrations and to check renal function.

RESULTS

Energy intake was higher than REE by a factor of 1.29, but it was lower than the energy requirement. Energy intake, adjusted for differences in body weight, was independent of sex, highest in those who were malnourished (defined as a body mass index (BMI) <21), and lowest in patients who scored poorly on the Mini-Mental State Examination. Energy intake and REE were independent of plasma CRP, creatinine, and albumin concentrations, as well as the initial diagnosis. REE was similar in men and women, at 18.8 kcal/kg per day. REE was 21.4 kcal/kg per day in patients with a BMI of 21 or less and 18.4 kcal/kg per day in those with a BMI greater than 21 kg/m2. The Harris-Benedict equation accurately predicted mean REE.

CONCLUSION

The mean REE of the geriatric patients studied was 18.8 kcal/kg per day, whereas energy intake was just sufficient to cover minimal requirements. Thus, hospitalized elderly patients are likely to benefit from higher calorie intake.

Oral supplements differing in fat and carbohydrate content: effect on the appetite and food intake of undernourished elderly patients

BACKGROUND & AIMS

Since fat, relative to other macronutrients, has low satiety and high energy density, it may have therapeutic application for supplementing energy intake. This study compared the effect of isoenergetic (1050 kJ) high fat or high carbohydrate oral supplements, given at breakfast, on the short-term appetite and energy intake in undernourished elderly subjects.

METHODS

Sixteen hospitalised, undernourished (body mass index: 20 +/- 3 kg/m2), elderly (77 +/- 8 yr) people were randomly allocated to a control or 1 of 2 supplement groups [fat: carbohydrate: protein (% energy) was 70:25:5 or 25:70:5]. In each group, energy intake (24-h food consumption) and appetite (visual analogue scales) were assessed over 3 consecutive days.

RESULTS

Mean energy intake significantly (P = 0.0035) increased following supplementation: high fat 6973 kJ/d, high carbohydrate 6906 kJ/d vs. control 6079 kJ/d but mean voluntary 24-h energy intake remained unaffected. Compared to controls, supplemented subjects experienced reduced hunger (P = 0.07) between breakfast and lunch, but showed no difference over the whole day (P = 0.55).

CONCLUSIONS

Under these study conditions a 1050 kJ oral supplement, irrespective of macronutrient composition, does not cause voluntary short-term energy intake compensation in undernourished elderly people.

A novel technique to demonstrate disturbed appetite profiles in haemodialysis patients

BACKGROUND

Malnutrition is common among dialysis patients and is associated with an adverse outcome. One cause of this is a persistent reduction in nutrient intake, suggesting an abnormality of appetite regulation.

METHODS

We used a novel technique to describe the appetite profile in 46 haemodialysis (HD) patients and 40 healthy controls. The Electronic Appetite Rating System (EARS) employs a palmtop computer to collect hourly ratings of motivation to eat and mood. We collected data on hunger, desire to eat, fullness, and tiredness. HD subjects were monitored on the dialysis day and the interdialytic day. Controls were monitored for 1 or 2 days.

RESULTS

Temporal profiles of motivation to eat for the controls were similar on both days. Temporal profiles of motivation to eat for the HD group were lower on the dialysis day. Mean HD scores were not significantly different from controls. Dietary records indicated that dialysis patients consumed less food than controls.

CONCLUSIONS

Our data indicate that the EARS can be used to monitor subjective appetite states continuously in a group of HD patients. A HD session reduces hunger and desire to eat. Patients feel more tired after dialysis. This does not correlate with their hunger score, but does correlate with their fullness rating. Nutrient intake is reduced, suggesting a resetting of appetite control for the HD group. The EARS may be useful for intervention studies.

Factors affecting energy and macronutrient requirements in elderly people

OBJECTIVES

(i) to describe energy and macronutrient requirements in healthy and diseased elderly patients from knowledge acquired about the age-related changes in energy balance (ii) to describe changes in body composition and the consequences of physical activity and exercise programs.

RESULTS

Aging in individuals considered healthy is associated with a reduction in muscle mass and strength (with consequences on autonomy), and an increase in fat mass mainly in the central area, the latter might increase the risk of cardiovascular disease. Body composition changes can be seen as a positive energy (fat) balance. The reduced fat-free mass is responsible for a low resting metabolic rate. Therefore, energy requirements are reduced all the more since physical activity is decreased. A simple means for calculating individuals' energy requirements from estimated resting metabolic rate and physical activity is not yet available in a validated form and is much required. Protein requirements are still debated. Exercise programs can be implemented for increasing muscle mass and strength (resistance training) or for improving aerobic fitness and reducing fat mass (endurance exercise). It is not yet clear whether structured exercise programs or spontaneous physical activity have similar advantages. It is not known in which cases resistance, endurance, or a combination of both exercises should be recommended. The consequences of physical activity and exercise programs on energy and macronutrient requirements is not clear. Diseased elderly persons are prone to malnutrition which impairs clinical and functional outcome. Malnutrition is the result of an energy intake inadequate to match energy requirements. Literature is very short of data on energy requirements in diseased elderly persons, who are under the complex influences of stress (increasing resting energy requirements), reduced body mass and physical activity (reducing energy requirements), plus potential effects of drugs. Almost nothing is known about macronutrient requirements.

CONCLUSIONS

Further studies are required to enable calculations of energy and macronutrient requirements of individuals, especially diseased. More work has to be done to understand the energy imbalance in the elderly (healthy and diseased). Careful evaluations of physical activity and exercise programs are necessary.

Nutritonal evaluation of pemphigus foliaceus patients on long term glucocorticoid therapy

Our objective was to compare food intake and nutritional status of Pemphigus Foliaceus patients (PG) on long term glucocorticoid therapy to a Control Group (CG). Fourteen PG female inpatients receiving prednisone (0.33 +/- 0.22mg/kg) for at least 12 months and twelve CG subjects were submitted to nutritional evaluation, including anthropometry, urinary creatinine determination and serum biochemical measurements, besides 48-h-based food intake records. Groups were compared by Chi-square, Mann-Whitney and "t" tests. PG patients and CG were paired, respectively, in relation to age (24.7 +/- 14.1 vs. 22.0 +/- 12.0 years), body mass index (25.8 +/- 6.4 vs. 24.0 +/- 5.6kg/m2), daily protein intake (132.9 +/- 49.8 vs. 95.2 +/- 58.9g), and serum albumin (median; range) (3.8; 3.5-4.1 vs. 3.8; 3.6-5.0g/dl). However, PG patients had lower height-creatinine index (64.8 +/- 17.6 vs. 90.1 +/- 33.4%), and higher daily energy (3080 +/- 1099 vs. 2187 +/- 702kcal) and carbohydrate (376.8 +/- 135.8 vs. 242.0 +/- 80.7g) intakes. Despite high food, protein and energy consumption, PG patients on long term glucocorticoid therapy had lower body muscle mass than controls, while showing high body fat stores. These findings are possibly related to combined metabolic effects of long term corticotherapy and inflammatory disease plus corticosteroid-induced increased appetite.