Many of us complain of slaving away in the gym without seeing any benefit to our waistline. But scientists may finally have the answer to this phenomenon. Although it may seem counter-intuitive, research suggests exercising could cause people to gain weight.
A group of volunteers increased their portion sizes by nearly a quarter following a sweaty work out. Researchers believe people overindulge after a gym session because they believe they 'deserve it'. And this may explain why people can struggle to lose weight even after exercising regularly, they added.
The research was carried out by Loughborough University, which boasts Sebastian Coe, Paula Radcliffe and Clive Woodward among its sporting alumni.
'[When it comes to weight loss] aside from what we eat, a critical factor is how much we eat. The results of the present study suggest that knowledge of a future exercise session results in an increase in planned energy intake at a meal after exercise, at least in habitual exercisers,' study author and senior lecturer in nutrition Dr Lewis James said.
The researchers had 40 volunteers, half of which were women, take part in an aerobic class at least three times a week. Writing in the journal Appetite, the researchers said: 'Individuals chose a larger portion size - a 24 per cent increase in energy content of food served [after classes].
'This increase in planned energy intake might attenuate the negative energy balance induced by exercise, and consequently might reduce any weight loss with chronic exercise training.'
The participants also upped their lunch-time portions by 150 calories after working out, the research found. And the scientists warn repeating this at dinner would more than outweigh any benefit of exercising. Chocolate consumption was also up by 20 per cent, with the female volunteers helping themselves to slightly more than the men.
Speaking of the effect this has on people's figures, the researchers wrote: 'Typically, there is an initial weight loss. However, after this, the rate of weight loss attenuates, or weight becomes stable over time.
But when exercise is combined with a healthy diet, it is an effective way to lose weight, they stress.
