Doing more exercise is not a practical way to reduce weight for most people, according to a leading scientist, challenging the government’s approach to tackling the obesity epidemic.
Using data from the last 25 years, Professor John Speakman of Aberdeen University told the British Science Festival on Wednesday that the current obesity epidemic has been caused by people eating more, rather than doing less exercise.
Prof Speakman, director of Aberdeen’s Institute of Biological and Environmental Sciences, also challenged the idea that physical activity is more important than diet in weight loss, suggesting people should focus on eating less if they want to lose weight.
His research shows that, contrary to popular belief, levels of activity in the general population have not fallen since the 1980s.
By reviewing studies from this period that measured energy expenditure, his team have been able to demonstrate that overall physical activity rates have remained steady.
This is the result of “a number of compensatory factors, including increased enrolment in gyms and purchasing of exercise equipment,” according to Prof Speakman.
In contrast, data on food purchases show that the amount consumed, in terms of calories per person, has increased by 12 per cent in the UK and 22 per cent in the USA since the 1970s.
The amounts of exercise needed to reverse obesity are too much for most individuals to achieve, according to Prof Speakman.
“Someone with a body-mass index of 35 would need to walk for 4 to 5 hours every day to lower their BMI to a healthy weight,” he said, adding that they would have to maintain this level for the rest of their life.
The same reduction in weight by changing diet would require eating 30 per cent less food.
Commenting on the government’s current healthy living campaign, Change 4 Life, which recommends more exercise, Prof Speakman said: “While we should promote exercise for its other health benefits, if you want to reverse the obesity epidemic, that’s not the solution.”