Our sedentary lifestyle is making us weak – and fat. But there are ways to beat the sitting bulge, says Dr Michael Greger.

How Not To Die author Dr Michael Greger is back, with a deeply researched book on the Western world’s struggle to stay slim and fit.

How Not To Diet (Macmillan) is a treasure trove of science-based data and dietary research, translated into accessible, do-able advice. The American physician and nutrition expert breaks down a variety of approaches to weight loss, including how to structure a low-sugar, low-fat diet packed with anti-inflammatory foods. He then goes beyond food to explore the many other weight-loss accelerators available to us.

One of these chapters focuses on what’s been dubbed the “sitting disease” – the health risks associated with excessive sitting, at our work desks and in front of our computers, phones and TVs. In the following extract, Greger finds out what protects some people from the fat-gaining effects of over-eating and a sedentary lifestyle – and how everyone can benefit from an activity called NEAT…

Why do some people gain [weight] more than others? If you experimentally overfeed a group of people the same amount over the same time period, you might assume there would be some variation, but the actual range of variability is truly mind-boggling. In a famous study out of the Mayo Clinic, subjects ate 1000 extra calories every day for eight weeks with no added exercise. In some people, that extra 1000 calories translated into only about a spoonful of added daily body fat, whereas others gained more than a third of a cup of body fat every day. By the end of the eight weeks, there was a tenfold variation in fat gain – from under a pound [about 400g] in total to more than nine pounds [more than 4kg].

Hold on. Someone ate 56,000 extra calories and gained less than a single pound of body fat? There’s a law in physics that basically says calories can’t just disappear, so what happened? Let’s look at the energy balance equation again:

Body fat = food + beverages

– metabolism – exercise

– other movement

The exercise level for the study subjects was fixed at a steady, low amount, and it turned out their metabolisms didn’t change much. So the only way caloric intake could shoot up without depositing as body fat would be if “other movement” shot up as well. And that’s what happened. The secret to eating in excess of 50,000 calories without gaining weight is NEAT: non-exercise activity thermogenesis.

NEAT is the heat given off by our regular activities of daily living, such as standing, moving and fidgeting. On average, fewer than 400 of those extra 1000 calories consumed each day of the study ended up being stored as fat. The bulk was burned off, particularly from a spontaneous increase in movement. One participant inadvertently started moving so much that an extra 692 calories burned off in a day. That’s like spending a quarter of your waking hours in motion.

You’d think overfeeding might lead to the opposite: inactivity. I imagine someone crashed on the couch rubbing their swollen belly. But no – when people are fed 1000 extra calories a day, a strange thing happens. They spontaneously start to move more out of some instinctual drive. This could be in the form of fidgeting or gesticulations, a restlessness leading to frequent standing or pacing, using up as many as hundreds of extra calories on average over the course of a day. Basically, NEAT is the sum of calories burned by everything we do that is not sleeping, eating, or sports-like exercise.

So the primary reason some people gain more weight than others despite eating the same amount of food is that they go weak in the NEAT. Easy gainers just don’t intuitively start moving more to compensate for the extra calories. Indeed, a NEAT deficit has been identified in obesity. Studies show obese individuals tend to remain seated for about two and a half hours longer each day than the average, inactive yet lean, shoestring couch potato. Normal-weight individuals just tend to get up and move around more.

After fitting “sedentary” people with sensors that tracked their posture and movement, researchers were surprised to find they in fact were walking the equivalent of seven miles a day (11.2km). That distance was just split up into dozens of stints lasting a few minutes at a time simply ambling around throughout the day. Remarkably, those small moments of movement can add up to more than 2000 calories a week, which just so happens to be what those overfed study subjects started burning up and about what you’d get from the hour-a-day exercise recommended for weight loss.

Just by subtly moving around more, your body can drain off as many calories as pounding it out an hour a day at the gym. Remember those extra 692 calories a day burned off by the study subject who had inadvertently started moving more? That’s more than you might burn rock climbing for an hour. Given its demonstrated power, if our bodies aren’t going to move more unconsciously, then maybe we should make a conscious effort to accrete some NEAT.