Zoe Harcombe’s book The Obesity Epidemic makes some valuable points, but some pretty dubious points too.
I’m going to focus here on chapter 14 entitled “Do More – The Role of Exercise”. In a nutshell, Zoe Harcombe thinks that structured exercise has no useful role to play in tackling the obesity epidemic, and that our sedentary lifestyles are not a major factor in the western world’s rising levels of obesity.
As a personal trainer who has helped several obese clients in London to lose weight with regular exercise (and healthy diet), I know how important exercise is, but Zoe Harcombe emphatically does not. Is it possible to be an obesity expert without understanding the value of exercise?
Zoe Harcombe criticises the Department of Health document ‘At Least 5 A Week’, published in 2004, written by Sir Liam Donaldson, chief medical officer, in which he says:
“It is only recently in human evolution that energy expenditure (primarily searching for sustenance) has not been inextricably linked to energy intake. With the industrial revolution and more recently the emergence of technological advances, a serious mismatch has emerged between food availability and the energy required to access food, leading to a new pandemic of obesity and type 2 diabetes.” (Liam Donaldson)
Zoe Harcombe thinks that reduced activity levels are not the main problem. The main problem in her view is our excessive consumption of processed carbohydrates. She is convinced that exercise cannot undo this damage.
She is also convinced that it’s carbs in particular, not excessive consumption of food in general, that is the culprit. She says:
“Had people consumed the same number of calories in the form of zero carbohydrate foods, they would have been unable to store fat and therefore would not have gained weight regardless of activity levels.” (Zoe Harcombe)
I think there are several problems with Zoe’s argument. She misrepresents public advice to become more active as a statement that inactivity is the sole cause of obesity, which it clearly is not, nor is the public advice saying this. (Although interestingly the junk food industry is keen to identify inactivity as the main cause of obesity, to divert attention from their foods which are indeed the main cause of obesity).
And Zoe Harcombe is convinced that fat in the diet cannot make you fat, but she fails to explain where excess fat in her ideal zero carb diet goes if it is not burnt as energy. The answer is (not surprisingly) that it’s stored as body fat, but Zoe remains convinced that this is impossible in the absence of carbs. She seems to think that you can eat as much fatty food as you like, including foods high in saturated fat, do no exercise or activity, and gain no body fat – as long as you stick to a zero carb diet.
Zoe Harcombe criticises the links made between inactivity and obesity at a conference in June 2010 organised by the Association for the Study of Obesity called Physical Activity, Obesity and Health. She listened to the evidence, and concluded:
“No further evidence was presented throughout the day to even attempt to demonstrate that sloth had caused obesity or that activity will cure it.” (Zoe Harcombe)
Zoe has a very narrow view of concepts like cause and effect. It is possible that something (in this case inactivity) can be a contributory cause rather than the sole cause. So it is possible that inactivity can be contributing to obese people remaining obese. Yet she rejects the role of inactivity/activity/exercise because it is not the sole cause or the sole cure.
She is right to point out that processed carbs consumption is a major cause of obesity, which has the effect of obese people being less inclined to exercise. But she doesn’t recognise that cause and effect can work in a downward spiral, in this case inactivity becoming a contributory cause of obese people staying obese.
It is true that you cannot out-train a bad diet, but Zoe takes this to the extreme of saying that exercise has no useful role to play in curing obesity. She points to empirical research that concludes that it’s not just inactivity that’s caused the obesity epidemic, to support her argument. She keeps falling into the same trap of false logic. Just because inactivity not the sole cause, doesn’t exclude it from being a contributory cause.
Here’s a typical Zoe Harcombe statement, which sums up her approach:
“Fat storage depends on carbohydrate and insulin. It cannot be caused by watching television.”
Zoe Harcombe is dead against going to the gym, or running, or any kind of “unnatural exercise” as she calls it. She says it has no benefit for weight loss, it wears you out so you cut down on other activity, and makes you hungry so you eat the wrong foods and gain fat.
“Those who regularly go to the gym and participate in scheduled exercise classes, often have little energy and inclination to be active at other times. They report going to the gym on the way home from work and then collapsing on the sofa all evening. Those who don’t have the time (or inclination) to go to the gym are more often active throughout the day.” (Zoe Harcombe)
I know from personal experience and the experience of my personal training clients in London that this statement is nonsense. If you perform a varied range of exercise at the gym, you actually gain energy. You sleep better, and you wake more refreshed and energised. Exercise relieves stress, and stress hormones contribute to weight gain, so anything that gets stress hormones under control is a good thing for weight loss.
With resistance exercise you build more muscle which makes you metabolically more active so you burn fat even at rest, and the increased muscle makes you more efficient and effective in physical tasks. You burn excess fat and this makes it easier to move around (there’s an old saying that you carry fat, but your muscles carry you).
And exercise gives you greater aerobic capacity, ie- your heart and lungs and circulatory system are more efficient at transporting oxygen to your muscles. This boosts your capacity for physical activity. Vigorous exercise also boosts your insulin sensitivity, enabling you to metabolise carbohydrates more efficiently. But Zoe Harcombe advises people to “cut both the carbs and the unnatural exercise.”
Zoe Harcombe makes the fatal error of seeing exercise only in terms of burning calories while performing the exercise itself. She ignores the after-burn effect of high intensity exercise, where calories are burnt for several hours afterwards. But more significantly, she ignores the effect of having more muscle mass on your basal and resting metabolic rate. You burn more calories at rest, 24 hours a day. This is ironic, as she spends the majority of the book criticising people for ignoring the significance of basal and resting metabolic rate, yet she ignores it herself when she discusses exercise.
“My personal view on exercise is, just as I think that we should eat as we have evolved to eat, I advocate doing what we have evolved to do. I do not believe that there is anything natural about running marathons, pumping iron, or spinning on stationary bikes.”
Zoe Harcombe’s public health message in relation to activity is to move naturally, and avoid all ‘unnatural exercise’. She recommends:
“Walk, talk, dance, sing, cook, clean, and tend the land, is a fair summary of what we should do.”
Ironically, she says we should go back to the natural activity of caveman times. If cavemen had limited themselves to the activities on her list, the human race would have died out hundreds of thousands of years ago. Cavemen had to run (both to escape from predators and to catch food), throw rocks and spears, climb, swim, fight, chop wood, lift heavy objects, and many other physically demanding activities. This is pretty much what a decent gym will mimic: swimming pools, weights rooms, pull-up bars, throwing medicine balls, boxercise and martial arts, treadmills.
If our range and intensity of activity were restricted to Zoe’s recommended list, we would be a physically weak and unfit nation indeed, and one vital weapon (real exercise rather than just daily activity) in the against obesity would be lost.