Washington: Thinking of hitting the gym to maintain weight? Scientists say exercise may not help you keep those extra kilos at bay, contradicting the belief that lack of physical activities or increased sedentary time is linked to obesity.
Physical activity has many proven health benefits, ranging from reducing the risk of heart disease, diabetes and cancer to improving mental health and mood.
People who are physically active tend to be healthier and live longer. However, while physical activity burns calories, it also increases appetite and people may compensate by eating more or by being less active the rest of the day.
"Our study results indicate that physical activity may not protect you from gaining weight," said lead author Lara R Dugas, assistant professor at Loyola University in the US. Some experts have suggested that a decline in physical activity, especially in the workplace, has been a key contributor to the obesity epidemic.
However, studies in which physical activity is objectively measured and participants are followed over time, has not found a meaningful relationship between weight gain and physical activity. Researchers followed adults aged 25 to 40 living in five countries: the US, Ghana, South Africa, Jamaica and Seychelles.
Previous research has found that when people are asked about their physical activity, they tend to overstate the amount they do. To provide a more objective measure, participants wore tracking devices called accelerometers on their waists for a week. The devices measured the wearers' energy expenditure and
Researchers also measured participants' weight, height and body fat. After an initial exam, participants were asked to return one year and two years later. At the initial visit, Ghana participants had the lowest average weights (63 kilogrammes for both men and women), and Americans the highest weights (91 kilogrammes for women, 93 kilogrammes for men).
Ghanaians were also fitter than Americans. Seventy-six per cent of Ghanaian men and 44 per cent of Ghanaian women met the US Surgeon General physical activity guidelines, while only 44 per cent of American men and 20 per cent of American women met the guidelines. The guidelines recommend doing at least two and a half hours of moderate-intensity aerobic exercise (such as brisk walking) per week.
Surprisingly, total weight gain in every country was greater among participants who met the physical activity guidelines. Researchers did not find any significant relationships between sedentary time at the initial visit and subsequent weight gain or weight loss. The only factors that were significantly associated with
weight gain were weight at the initial visit, age and gender. The study was published in the journal PeerJ.