Weight loss: the futility of the exercise

This coming Sunday, tens of thousands of people will reach the culmination of months of hard training by running, and (hopefully) completing, the London Marathon. For them, the 26 miles 365 yards from Blackheath and Greenwich to The Mall will follow many hundreds of miles of slogging round streets and parks in preparation. At the end, there will be the satisfaction of an enormous achievement, a triumph of endurance over fatigue and, for many, a refusal to concede to painful legs and blistered feet. But for the vast majority, the one thing they won’t have achieved is significant weight loss.

Take this from the Runner’s World forums: ‘I am getting really upset that I’ve actually gained weight running 30-50 miles weekly. This is my first time training for a marathon. Prior to this, I always ran 15-20 miles a week, cycling, pilates classes, weights, etc. Since the training started I’ve had less time for other forms of exercise. I’ve put on almost 10 lbs in 4 months.’ Other users then chip in to concur: despite all expectations, running a marathon seems to make you fatter or, at least, not very much thinner.

The fitness writer for The Times (London), Peta Bee, has had a similar experience. In Saturday’s edition, she wrote: ‘On New Year’s Day I started training for the London Marathon and have since become your archetypal running bore, reeling off statistics about my state of body and mind to anyone who will listen. Come race day, April 17, I will have run for 107 consecutive days, totting up an average 45 miles a week and regularly clocking 15 miles or more in a single hit… I have yet to lose a single pound.’

As a fitness fanatic, Bee was unlikely to be carrying many spare pounds anyway. But there’s plenty of scientific research which backs up these anecdotes. A study published in 2007 in the Journal of the American Medical Association shows that even large women achieve little weight loss through exercise. The study followed 464 sedentary women aged between 45 and 70 who undertook a range of different levels of exercise. While the exercise clearly made them fitter, and probably had a number of health benefits, it didn’t make them skinnier. The authors note that ‘we observed no changes in weight or body fat percentage’, though they add that it is ‘well documented that exercise without dietary intervention has limited effectiveness in producing substantial weight loss’.

There’s no doubt that if you run long distances, you burn a lot of calories – about 100 calories per mile. So if you run 50 miles per week, that’s the calorific equivalent of perhaps two days normal food consumption. If you can manage to avoid eating extra food to compensate for that mileage, you should be able to lose weight. But most people simply get hungry – probably ravenously so in the case of those who can run large distances – and eat more.

Of course, there is individual variation. There’s always someone who can claim to have gone from chubby to skinny thanks to pounding out the miles. Whether such people really have just changed their exercise habits without also changing their eating habits is open to debate. But for most people, the effect of trying to run your butt off is that your butt remains as large as ever.

This observation has wider implications. We are constantly assured that the ‘obesity epidemic’ is a product of an ‘obesogenic’ environment. Thanks to cars and other forms of transport, sedentary jobs, labour-saving devices and a decline in informal physical activity, we have become a society of ‘couch potatoes’. We’re eating as much as ever, so the theory goes, but we’re not burning it off. What we need is greater exhortation to get active, more physical education in schools, and NHS-funded vouchers for the local gym and swimming pool.

But just how much exercise do the proponents of this thesis think we’re capable of doing? If training for and running a marathon – far and away the biggest physical challenge most participants will ever undertake – is incapable of shifting the pounds, what effect is a much smaller amount of exercise ever likely to have? The answer is none. Like flies banging our heads against a window pane, the sheer futility of the exercise doesn’t stop us from trying again and again.

Even when people do lose weight, the weight loss only lasts as long as their new habits. As soon as the running stops or the food intake starts creeping up, the flab reappears.

As I’ve noted before on spiked, a more persuasive outlook is that what we eat matters considerably more than how much we eat or how many calories we burn off in exercise. The idea of an obesity epidemic has been somewhat exaggerated – particularly in the sense that being fat is considered to be a death sentence. To the degree that obesity is a problem, however, it is probably due to a shift in our diets in recent decades towards eating more highly refined carbohydrates. Moralising about our lifestyles won’t achieve anything, nor will the mainstream advice to simply eat less food. For those with a tendency to seriously pile on the pounds, avoiding carbohydrate-rich foods seems more likely to be effective.

The best of luck to everyone running on Sunday. I hope you get what you want – a first marathon completed or a personal best achieved – without too much pain along the way. The only thing I’d like to see exhausted is the idea that the rest of us need to be whipped into shape.

Rob Lyons is deputy editor of spiked and blogs at Panic on a Plate.