Genes may be the key factor in determining how active a person naturally is, suggests a new study of “couch potatoes”. But the research also suggests health authorities can tackle the growing obesity epidemic by promoting simple activities like standing up and walking.
Previous research has shown that casual activities like shopping and even fidgeting can keep people trim. Now, James Levine, a physician at the Mayo Clinic in Rochester, Minnesota, US, and colleagues have investigated what makes people prone to these behaviours, called “non-exercise activity thermogenesis” (NEAT).
The team designed undergarments fitted with sensors to study the posture and movements of 20 self-proclaimed “couch potatoes” for 10 days. Half of the participants were lean, while the others were mildly obese.
The team found that the obese people sat for about 2.5 hours longer per day than the lean people. That translates to an extra 350 calories for the same daily food intake and could mean that these “extreme” couch potatoes pack on an extra 15 kilograms per year.
Levine says the results show “you don’t have to join a gym or buy expensive equipment to lose weight – it’s available to you right now.”
The team then gave the lean people an extra 1000 calories a day and cut 1000 calories from the diets of the obese people for eight weeks. The obese people lost an average of 8 kg over that period, while the lean people gained about 4 kg each.
However, the change in diet did not produce a change in the activity of either group – obese people who had shed pounds still sat more than their newly chubby counterparts. That suggests genes ultimately determine how naturally active people are, says Levine.
If that is so, says Eric Ravussin of the Pennington Biomedical Research Center in Baton Rouge, Louisiana, US, people may have trouble increasing their NEAT through sheer force of will. “If it is genetically determined, there is little hope that recommending behavioural changes will help,” he told New Scientist.
Levine responds: “You could think doomsday – that there’s nothing we can do about obesity. However, obesity rates were almost negligible 50 years ago, yet the genes were the same. What has changed is our environment.”
Both researchers agree that environmental change toward a more sedentary lifestyle has contributed to the obesity epidemic, which causes 400,000 deaths per year in the US alone. Whether an individual is obese or not depends on the interaction of their genetic disposition and their environment.
Ravussin expects to see action in the future: “When obesity becomes too much of a burden to the health care system, changes to the environment will be imposed by the government.” These could include designing neighbourhoods to encourage walking between shops and making public transportation more accessible. Even short walks to a bus stop could increase a person’s NEAT, he says.
“When I saw the data, I bought a treadmill and mounted my computer workstation above it,” says Levine. He now spends most of his working day walking.
But he argues for even more dramatic changes. He envisions that cinemas could offer “standing” tickets and that employers could conduct meetings while standing or walking – methods already shown to reduce meeting length.
“Massive social change does occur where the will exists and the obesity problem is massive,” he told New Scientist.
Journal reference: Science (vol 307, p 584)