Study tips the scales in favour of exercise

People who are overweight or obese shouldn’t give up exercise even if they fail to lose much weight, according to a new study from the University of Leeds, which found the health benefits of exercise go well beyond dropping a dress size.

As part of the study, 58 overweight men and women completed a 12-week cardio-exercise regime, involving five supervised training sessions a week, designed to burn 500 calories each time.

By the end, some individuals had lost up to 14.7kg in weight, the average weight loss was 3.7kg, while others lost less weight than expected. But most surprisingly, five people had actually gained 1-2kg. Clearly then, regular exercise doesn’t have the same effects on everyone.

However, Professor John Blundell from the Leeds BioPsychology Group said what is more significant is that all of the participants reaped the benefits of a drop in blood pressure, reduced body fat, a smaller waist, and a slower heart rate.

“The results showed that although there were great variations in weight loss between individuals, you still get a lot of extra benefits from doing exercise that you wouldn’t get from dieting alone, even if you don’t lose any pounds,” he said.

Dr Neil King, the co-principal investigator, added: “Everyone who took part in this study was able to exercise at a higher intensity level, so they all got fitter. For example, their maximum oxygen consumption, called VO2 max, increased by an average of 20% after just 12 weeks. So on balance, it’s probably better to be fit and overweight, rather than slim but unfit.”

Most astonishingly, even in the group of people who lost little or no weight, their blood pressure dropped significantly, and they typically lost 3.7cm off their waist circumference, which is equivalent to one dress or trouser size.

“Waist circumference indicates how much fat you carry in your abdomen area, which is a strong risk factor for heart disease in men and women,” he explained. They also burned off between 1.5% and 3.5% fat mass and gained lean tissue, so their body composition was visibly changing.

The findings of the BBSRC-funded study were published last month in the International Journal of Obesity. The other Leeds researchers involved were Mark Hopkins and Phillipa Caudwell, together with academics from the Queensland University of Technology in Brisbane.

This is the first time that a major exercise study has monitored people during training sessions to ensure they all did exactly the same workout. Often exercise fails to produce a desired weight loss because of lack of compliance.

Professor Blundell said the results suggest that biological differences may partly be to blame for obesity, as in some individuals physical activity can trigger a compensatory response and try to ‘steal back calories’ after exercise. For example, their body might respond to the energy deficit by stimulating their appetite, causing them to snack more on energy dense high-fat foods, being more inactive at other times of the day, or by slowing their metabolic rate.

“People often overestimate how much energy they have burned off through exercise,” he said. “To shed 600 kilocalories, for example, a moderately fit person would have to exercise for about 60 minutes. Yet it only takes three minutes to eat 600 kilocalories in the form of a piece of gâteau and a Danish pastry.”

The study also asked participants to wear heart rate monitors and activity meters every day to calculate how much energy they used at other times. The initial results suggest some people may involuntarily rest more before or after exercise to compensate for the energy deficit.

“We strongly advocate the role of exercise in weight management, however, its effectiveness will vary between individuals.

Our results suggest that the body’s response to exercise can act as a major barrier to weight loss, so some people probably won’t lose weight through exercise alone, and may need extra help to keep their appetite in check,” said Professor Blundell.

The challenge now for science is to figure out why exercise helps some people lose weight but not others. The research team have collected a large number of blood samples to look for the presence of certain peptides known to influence human appetite, and they suspect that physical activity may drive up these peptides.

“We’re also following up with the 58 people who did this study to find out if they’ve reverted to their original body weight or lost more weight. We’re starting the exercise sessions up again in January with a new group of volunteers and will be looking in greater detail at those who don’t lose any weight.”