People who want to lose meaningful amounts of weight through exercise may need to devote more than two-and-a-half hours a week to aerobic training such as running, walking or cycling, researchers say.
The finding emerged from a review of 116 published clinical trials that explored the impact of physical exercise on weight loss, waist size and body fat. In total, the trials reported data for nearly 7,000 adults who were overweight or obese, meaning their body mass index (BMI) was more than 25.
Analysis of the trials’ results showed that body weight, waist size and body fat all decreased as people did more aerobic exercise each week, but training for less than 30 minutes a day, five days a week resulted in only minor reductions, the researchers found.
“At least 150 minutes per week of aerobic exercise at moderate intensity is required to achieve important weight loss,” said Dr Ahmad Jayedi, an epidemiologist at Imperial College London, and first author on the study published in the medical journal Jama Network Open. For people who were overweight or obese, losing 5% of body weight in three months is regarded as clinically important, Jayedi said.
The NHS says all adults should do some type of physical activity every day. People aged 19 to 64 are urged to do at least two-and-a-half hours of moderate exercise, or 75 minutes of vigorous exercise, each week to keep fit and reduce the risk of conditions such as heart attack and stroke. The latest study suggests the same level of aerobic exercise is the minimum needed to achieve meaningful weight loss for people with a BMI of more than 25.
Jayedi acknowledged that the target might seem daunting for some, but urged people to find an exercise they could build into their daily routine. For example, people could increase the distance they walk by changing their route to work or hopping off the bus or train a stop earlier than usual, he said.
“Motivating people can be quite challenging, especially when it comes to altering their lifestyle and boosting their physical activity levels. Habits like consuming a lot of ultra-processed foods and having a sedentary life are deeply ingrained, making them tough to change,” Jayedi said.
“When it comes to exercise, all forms are beneficial, and we didn’t evaluate any differences among them. However, walking and running are excellent examples of aerobic activities that can easily fit into our daily lives,” he added.
The national health guidelines recommend people spread their exercise over the week, but recent studies have shown that “weekend warriors” who cram all their training into Saturday and Sunday reap similar health benefits. One study found that weekend warriors who fit a week’s worth of exercise into one or two days were less likely to develop more than 200 diseases than inactive people.
For people looking to lose weight, doctors recommend a healthy diet as well as regular physical exercise to ensure people are not consuming too many calories. Jayedi said a diet rich in whole grains, fruits, vegetables, nuts and fish, and low in red meat, sugary drinks and ultra-processed foods was helpful and reduced the risk of chronic diseases such as type 2 diabetes, cardiovascular disease and some cancers.
Last month, a report from the charity the Food Farming and Countryside Commission said that Britain’s growing addiction to unhealthy food was costing the country £268bn a year, more than the entire NHS budget. “Far from keeping us well, our current food system, with its undue deference to what is known colloquially as ‘big food’, is making us sick. The costs of trying to manage that sickness are rapidly becoming unpayable,” it said.
