It Is the Diet That Makes You Lose Weight, Not Hours of Exercise

Are we less active than we used to be?

It will give couch potatoes more reason to put their feet up — and disappoint those who hit the gym to shed extra pounds. According to Professor John Speakman of the University of Aberdeen, exercising is not the best way to lose weight: his research suggests we are not less active than we were decades ago, which means the obesity epidemic is driven by what we eat, not by how little we move.

Working with Klaas Westerterp of Maastricht University, Speakman surveyed decades of energy-expenditure data from the US and the Netherlands. The finding: despite our growing reliance on time-saving technology, daily energy expenditure has not declined since the 1980s. The average man still burns roughly 1,380 calories a day in activity, and the average woman about 950 — essentially unchanged. What has changed is intake, up by at least a third, to an average of around 3,500 calories a day. (Westerterp & Speakman, International Journal of Obesity, 2008.)

Why doesn't exercise fix it?

Factors that look like causes of weight gain do not necessarily equate to it. Fewer children walking to school, for instance, does not automatically mean less activity overall — children driven to school may simply spend more time running around in the playground. Evening television watching has largely replaced other sedentary activities like reading and listening to the radio, rather than displacing exercise.

Speaking at the British Science Festival in Birmingham, Speakman put it bluntly: "The idea that small changes in lifestyle are enough to offset obesity is wrong. In fact, enormous changes in energy balance are needed, and that can only realistically be achieved through changes in diet." His prescription: "We should be promoting exercise for health reasons, but weight is not realistically going to benefit from exercise. Dieting, on the other hand, does have an effect on energy intake, and this is a more realistic approach."

So what should you do?

None of this means exercise is worthless — it remains one of the best things you can do for your heart, your mood, and your longevity. But if the goal is specifically weight loss, the evidence points at the plate, not the treadmill. Ayurveda reached a similar conclusion centuries earlier, placing digestion at the center of health; Swastik's comparison of triphala and isabgol explores how the tradition supports everyday gut regularity — one small, practical piece of the dietary puzzle.