Why exercise is not a cure for obesity and what works better for those seeking to shed weight in the long term

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The on-line version of the British Medical Journal recently published a study in which the effects of exercise on body weight was assessed in some 545 children with an average age of 4 [1] The children exercised for 30 minutes, three times a week. Basically, this additional exercise made no difference to their weight. The bottom line is that this research suggests that exercise alone won’t prevent the burgeoning rates of obesity we’re seeing in kids.

Further prompting to write a blog about this has come from news stories circulating this morning a story about how we in the UK are the fattest people in Europe. Apparently, one in five of us are now clinically ‘obese’.

There is a constant refrain in weight loss circles that goes something along the lines of: ‘if you want to lose weight you need to eat less and exercise more.’ But what are the relative merits of these approaches? The recent BMJ study suggests that exercise may have a somewhat limited role in healthy weight maintenance. Actually, this in line with other research which shows that, as far as weight loss is concerned, exercise is not particularly effective. For instance, one review found the often-prescribed 3-5 hours per week of moderate to vigorous activity is likely to have very little impact on weight [2].

This may come as a bit of a shock, but it probably won’t be to anyone who has exercised in a gym on a piece of equipment that counts ‘calories burned’. Most people who have endured this sort of torture will know that those calories notch up very slowly indeed. And at the end of the workout it might have occurred to those individuals that half a choccie bar wolfed down in less than a minute is enough to undo all that good work that has gone on for the last half an hour or so.

There is some other support for this idea from a study that was published earlier this year in the American Journal of Nutrition [3]. In this research, the relative role of calories intakes and calories burned were assessed with regard to their role in the body weight in children. They found that 74 per cent of variation in weight was down to the calories consumed, rather than those burned. This reinforces the idea that if we’re looking to lose or maintain our weight, then it’s the diet we need to look to in the main.

Personally, I’m not into ‘portion control’ or counting calories, but I do believe it helps for people to eat in a way that puts a natural brake on the appetite. In general terms, this means eating regularly, and it also means eating foods that release sugar relatively slowly into the bloodstream (what are known as low glycaemic index or low ‘GI’ foods). Basically, the lower a food’s GI, the more satisfying it tends to be. Of 20 studies published between 1977 and 1999, 16 showed that low GI foods promoted the satisfaction derived from that meal and/or reduced subsequent hunger [4]. Overall, the results of the studies in this area show that an increase in the GI by 50 per cent reduces the satisfaction it gives by about 50 per cent! This has obvious and profound implications for anyone wanting to curb a tendency to overeat. Low GI foods include meat, fish, eggs, most fruits and vegetables (other than the potato), beans, lentils and nuts. High GI foods include most starchy carbs such as bread, potato, rice, pasta and breakfast cereals. In general terms, reducing these foods in the diet seems to allow people to be less hungry. In practice, I’ve found this usually helps individuals make lasting changes to their diet.

I’ve attached here a couple of articles that explore the concepts of regular eating and expands a little more on the benefits of not filling up on those starchy staples we’re so often told to base our diet on.


1. Reilly JJ, et al. Physical activity to prevent obesity in young children: cluster randomised controlled trial. BMJ, doi:10.1136/bmj.38979.623773.55 (published 6 October 2006)

2. Votruba SB, The role of exercise in the treatment of obesity. Nutrition. 2000 Mar;16(3):179-88

3. Swinburn BA, et al. Estimating the effects of energy imbalance on changes in body weight in children. Am J Clin Nutr 2006 83(4):859-863

4. Roberts SB. High-glycemic index foods, hunger, and obesity: is there a connection? Nutrition Review 2000 58:163-169

Observer Column – 20th July 2003

Many of us will be looking forward to taking some foreign sun this summer. However, the thought of revealing our bodies on the beach or by the pool can also make us mindful of the fat we laid down during the winter. This time of year will see lots of us looking to trim our figures by trimming our diets, and eschewing between-meal snacks is a common weapon used in the fight on fat. However, I recently glimpsed a TV advert for a popular range of slimming foods that encourages us to eat up to six times a day. I suspect many will be intrigued by the notion that, far from putting us at risk of piling on the pounds, snacking actually aids weight loss. The obvious reaction to a weight loss plan that encourages all-day eating is that it must be generous to a fault.

The idea that snacking can help us shed excess weight clearly runs contrary to the commonly-held belief that eating less and being hungry are almost prerequisites for weight loss success. Yet, while food deprivation may seem like a sensible strategy for slimming, my experience in practice is that is often fails to have the desired effect. Although many individuals seem to be able to exercise considerable dietary restraint between meals, they may also fall foul of a ravenous appetite at mealtimes, especially supper. Those who cut down on the frequency with which they eat may simply make up for this when they do.

There is a thought that, by helping to keep our appetite under control, snacking might actually help us to eat less, not more. Although somewhat counter-intuitive, there is actually some evidence for this concept. In one study, men were fed a set meal, and five hours later were asked to eat freely from a buffet. At another time, the same men were given a fifth of the set meal each hour, before being presented with the same food free-for-all. On both occasions, the researchers measured the number of calories consumed at the buffet. Compared to the single meal, frequent feeding was associated with a reduction in average calorie intake of more than a quarter.

The ability of regular eating to reduce meal size has other important implications for our weight. Generally speaking, the more we eat at one sitting, the more of the hormone insulin we are likely to secrete to temper the rise in blood sugar that comes after a meal. While insulin is essential to life, it has anabolic (weight-gaining) effects in the body. One of insulin’s chief actions in the body is to stimulate the conversion of sugar into fat ” not ideal for those wanting to trim down a little. High levels of insulin are also believed to stimulate the appetite, specifically for blood sugar-boosting foods that will tend to cause more surges of fat-inducing insulin.

Despite its undesirable reputation, there is good reason to see snacking as useful strategy for weight loss. A piece or two of fresh fruit and/or a handful of nuts had in the mid-morning and late afternoon can take the edge of our appetite, and lead to the consumption of more moderately sized meals that are less likely to be sequestered as fat around the body. For those of us seeking to slim down this summer, it’s worth bearing in mind that going hungry between meals is only likely to cut our losses.

Observer Column – 13th June 2004

The Government has recently come under considerable criticism for its flabby attitude to the ballooning rates of obesity in the UK. However, even if the politicians weigh into this area, my sense is that reversing our growing epidemic will be akin to turning the Titanic: the situation that we have taken a few decades to get into could quite easily take a few decades to get out of. I suspect many of us aiming to live in reduced circumstances will be wanting results more rapid than those that might be achieved through political leadership and legislation.

Statistics show that, at any time, about one in four of us is exercising some personal responsibility in this respect by putting ourselves on a diet. This figure will almost certainly bulge at this time of year as many of us face the prospect of revealing our beach bums and tums. For most, the investment made in terms of dietary restraint will be repaid in the form of lost pounds. However, the chances are that a year on, most would-be slimmers will find themselves no lighter than they are now, and may even have gained a few pounds in interest. The problem for so many is not losing weight, but keeping it off.

While the reasons for weight regain are complex, the primary cause of this phenomenon is almost certainly the return of individuals from a restricted regime to their default diet. Our dietary predilections are notoriously resistant to change in the long term, so I was interested to read a recent report which suggests that many individuals who have come off a carbohydrate-restricted diet (such as Atkins), continue to eschew fattening foodstuffs such as soft drinks and confectionery in their everyday lives.

This report seems to offer a glimmer of hope for those seeking to shed pounds permanently, because there is good reason to believe that long-term restriction of specific carbohydrates can offer enduring weight loss. Eating less carbohydrate ensures that the body makes less insulin – a hormone that predisposes to the deposition of fat in the body and at the same time stalls the body’s fat burning potential. There are now several studies which show that restriction of carbohydrate is generally more effective in bringing about weight loss than diets that are low in fat. Considerable evidence now exists which shows that, compared to standard low-fat approaches, low-carbohydrate eating brings about favourable changes in blood fats such as higher levels of ‘healthy’ high density lipoprotein (HDL) cholesterol and lower levels of unhealthy triglycerides.

Just last month, two studies were published in the Annals of Internal Medicine which bore out the advantages of lower carb eating. Tellingly, one of these studies found that individuals ascribed to a low-carb diet were better able to stick to the regime than those on a low-fat plan. This finding mirrors my own experience in practice that many individuals find eating less refined sugar and grain-based starches like bread, breakfast cereals, pasta and rice quite sustainable, and can look forward to long-term weight loss as a result. Basing the diet on natural, unprocessed foods which tend not to disrupt the body’s biochemistry (such as meat, fish, eggs, fruit, green vegetables, nuts, beans and lentils) really does seem to help ensure that weight shed this summer remains long lost.

More To Explore

Walking versus running

I recently read an interesting editorial in the Journal of American College of Cardiology about the relative benefits of walking and running [1]. The editorial

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