Cutting calories is generally regarded as the best way to lose weight.
But a new study from Harvard University suggests that, in the longer term, exercise is the best and the only way to keep weight down.
As anyone who has tried to lose a meaningful amount of weight will know, shedding the pounds in the first place is the – relatively – easy bit. Keeping them off is an even greater challenge.
Now, the first study to comprehensively examine the seven most commonly practised “weight-loss strategies” (WLS) finds that there is simply no substitute for exercise, in the longer term.
That is partly because it is harder to keep up a diet than it is to carry on exercising – while regular exercise fundamentally changes the way the body works in a way that helps to sustain weight loss, researchers suggest.
Harvard University researchers studied the effect of seven ways to lose weight over the course of three decades, looking at people who lost 4.5kg or more as a result of their chosen weight loss programme and focusing mainly on those who are obese and overweight.
They looked at low-calorie diet, exercise, low-calorie diet plus exercise, fasting, commercial weight loss programme, diet pills and a combination of fasting, commercial and diet pills (FCP).
And they found that the obesity exercise group, who had opted for regular walking, running, cycling, and other aerobic activities, as their method for shedding the pounds, were most likely to keep the weight off.
This group recorded a 4.2 per cent decline in weight, on average, after four years – compared to a 2.5 per cent weight loss in overweight people, and 0.4 per cent decline in lean people.
By contrast, obese people who focused on fasting, commercial and diet pills (FCPs) lost only 0.3 per cent of their weight over the same period, while overweight people gained 2 per cent more weight and lean individuals put on an extra 3.7 per cent.
Calorie cutters, meanwhile, were the next least successful group over the four years among obese participants – a finding that tallies with a previous study in the journal of the Academy of Nutrition and Dietetics, which found that after a one-year “intervention” a group of dieters had lost 6.8kg but after another year they had regained 7.7kg.
“Weight maintenance after weight loss is notoriously challenging. We found that most individuals who had lost at least 5 per cent of body weight using diet, diet and exercise, or cognitive behavioral treatment
regained that weight,” said Qi Sun, of Harvard T.H. Chan School of Public Health.
Dr Sun said it’s unclear exactly why exercise is the best way to lose weight in the long term but believes it is a combination of practicality and science – for example by helping the body to counteract some of the weight-gaining processes that are triggered after the loss of a few pounds as it seeks to compensate for the loss of calories it is used to, such as burning energy at a slower rate.
“A series of compensatory physiological adaptations favouring weight regain are triggered by weight loss, such as increases in orexigenic hormones (such as ghrelin) and fat accumulation and decreases in anorexigenic hormones (such as leptin, cholecystokinin, peptide YY) and energy expenditure,” he said.
“Exercise was demonstrated to mitigate weight regain by counteracting some of these adaptations. For example, exercise has been reported to restore the hormone perturbations and increase energy expenditure and fat oxidation.
“In addition, exercise was suggested to help weight maintenance by breaking the vicious cycle of stress and obesity [from the resulting comfort eating]. And, importantly, exercise might be more sustainable.”
He pointed to a separate weight loss trial in the Journal of the Academy of Nutrition and Dietetics, which showed that 44 per cent of participants in the exercise group reported exercising often after starting to try to lose weight, but only 6.7 per cent in the diet group reported adhering often to dietary recommendations.
David Ray, Professor of Endocrinology at Oxford University, who was not involved in the research, said the study was “important and nicely done…The gain in effect you get with exercise is powerful”.
He cautions that the study is “observational”, meaning that there could be other reasons for weight loss beyond the methods participants used to lose weight. But he he says the researchers have taken care to factor in “confounding” factors where they can, to establish as clear a cause-and-effect as they are able.
The researchers used data on almost 200,000 people aged from 24 to 78 from three long-running studies between 1988 and 2017.
The study also showed that individuals with obesity who attempted to lose weight, regardless of the WLSs used, tended to gain less body weight and have a lower diabetes risk.
Emma Elvin, senior clinical adviser at Diabetes UK, said: “Living with overweight or obesity are important risk factors for type 2 diabetes , but while increasing exercise levels can help with weight loss, this alone is not the most effective way to lose weight. However, with the right support, through combined lifestyle interventions including diet, physical activity and weight loss, up to half of cases of type 2 diabetes can be prevented or delayed.”
“It’s important to remember that there’s no ‘one-size-fits-all’ diet for people living with, or at risk of type 2 diabetes. Diets such as lower-carb or Mediterranean can help some people with or at risk of type 2 diabetes to lose weight, but ultimately the best diet is one that is nutritionally balanced, that you can stick to in the long term.
“If you’re living with type 2 diabetes and are thinking about making changes to your diet or physical activity, it’s important to do so with the support of healthcare professionals. For those at risk of type 2 diabetes, your healthcare team can signpost to appropriate support and prevention programmes,” she said.
The research is published in the journal PLOS Medicine.
How the seven types of weight loss strategy fared after four years among obese people (from best to worst):
2 Low-calorie diet & exercise
3 Diet pills
5 Commerical Weight loss programme
6 Low-calorie diet
7 Fasting, commercial and diet pills (FCP)