Exercise counteracts the effects of short-term overfeeding and reduced physical activity independent of energy imbalance in healthy young men


D. Thompson: Department for Health, University of Bath, Bath BA2 7AY, UK. Email: d.thompson@bath.ac.uk

Key points

  • • Physical exercise significantly improves health but to what extent these benefits depend on altered energy balance remains unclear.
  • • In a human experimental model, we investigated whether daily exercise could counteract the effects of short-term overfeeding and under-activity independent of its impact on energy imbalance in healthy young men.
  • • Short-term positive energy balance from overfeeding and under-activity resulted in impaired metabolic outcomes and alterations in the expression of several key genes within adipose tissue involved in nutritional balance, metabolism and insulin action.
  • • These changes were mostly prevented by the addition of a daily vigorous-intensity exercise bout even in the face of a standardised energy surplus.

Abstract  Physical activity can affect many aspects of metabolism but it is unclear to what extent this relies on manipulation of energy balance. Twenty-six active men age 25 ± 7 years (mean ± SD) were randomly assigned either to consume 50% more energy than normal by over-consuming their habitual diet for 7 days whilst simultaneously restricting their physical activity below 4000 steps day−1 to induce an energy surplus (SUR group; n= 14) or to the same regimen but with 45 min of daily treadmill running at 70% of maximum oxygen uptake (SUR+EX group; n= 12). Critically, the SUR+EX group received additional dietary energy intake to account for the energy expended by exercise, thus maintaining a matched energy surplus. At baseline and follow-up, fasted blood samples and abdominal subcutaneous adipose tissue biopsies were obtained and oral glucose tolerance tests conducted. Insulinaemic responses to a standard glucose load increased 2-fold from baseline to follow-up in the SUR group (Δ17 ± 16 nmol (120 min) l−1; P= 0.002) whereas there was no change in the SUR+EX group (Δ1 ± 6 nmol (120 min) l−1). Seven of 17 genes within adipose tissue were differentially expressed in the SUR group; expression of SREBP-1c, FAS and GLUT4 was significantly up-regulated and expression of PDK4, IRS2, HSL and visfatin was significantly down-regulated (P≤ 0.05). The pAMPK/AMPK protein ratio in adipose tissue was significantly down-regulated in the SUR group (P= 0.005). Vigorous-intensity exercise counteracted most of the effects of short-term overfeeding and under-activity at the whole-body level and in adipose tissue, even in the face of a standardised energy surplus.