New research from Royal Holloway, University of London has found that changes in lifestyle over the past 30 years have led to a sharp reduction in the strenuousness of daily life, which researchers say may explain why there has been a dramatic rise in obesity.
The study, carried out by Dr Melanie Luhrmann from the Department of Economics along with Professor Rachel Griffith and Dr Rodrigo Lluberas, revealed that while obesity rates have almost trebled, surprisingly, our actual calorie intake has fallen by around 20 per cent compared to 30 years ago.
The researchers found our current lifestyle changes mean in spite of the smaller number of calories we put on weight as our lives have become more sedentary.
The study found that both men and women are more likely to work in less strenuous occupations than in the past. Work is important because it accounts for a large share of people's time but the academics also noted that how people spend time outside of work has also changed. For example, both men and women spend more time watching TV and more time commuting by public transport or car which are much less strenuous than walking or cycling.
The research also found a link between work and calories with many workers eating out more and purchasing less calories for home consumption. This suggests that the success of policy interventions aiming to reverse the rise in obesity by changing people's food purchasing behaviour may depend on taking interactions between work and calories into account.
Dr Melanie Luhrmann says: "Our research shows that decisions over work and food demand are related. First of all, because individuals that work substitute more towards market-produced food, for example, towards processed foods and eating out. Secondly, weight gain arises from a caloric imbalance, meaning if more energy is consumed than expended. Hence, both calories and physical activity are important in explaining the rise in obesity. People have adjusted their calories downwards, but not enough to make up for the sizable decline in physical activity. Part of this decline comes from reduced activity at work. So we should take into account the link between work and calories when evaluating policy interventions aimed at reducing obesity."