There are many reasons to exercise. Stronger abdominal, lower-back and core muscles help stabilise the spine, freeing us from the nagging irritation of lower-back pain. Cardio exercise such as jogging or aerobics makes your heart and lungs work harder, lowers the level of "bad" LDL cholesterol in your blood, strengthens bones and wards off high blood pressure and coronary heart disease. And regular cardio workouts have a profound impact on our mental health, combating stress, depression and anxiety. All these things, and more, we get from our thrice-weekly gym sessions or pre-work pavement-pounding.
But let's be honest here. The primary reason that most of us exercise is either to lose weight, or to maintain a body shape that we can bear glimpsing in the mirror. For reluctant exercisers, every gym session is a chore. We may dread the chill, the shrieking kids and the chlorine reek of the local baths, but dutifully haul ourselves up and down anyway, all to shed the love handles gained from one curry or beery night too many. We subject ourselves to the £30-an-hour bullying of our personal trainer to make up for that quiche we couldn't resist or that bottle of chardonnay chilling, seductively, in the fridge at home.
It's a simple, tried-and-tested equation: exercise equals weight loss. The foundations on which a multibillion-pound fitness industry is built. But what if that equation was wrong? Or, at least, a far more complex one than conventional thinking would have us believe?
A raft of recent blogs and articles have gleefully reacted to new research on the relationship between workouts and fat-burning, with headlines such as "Health Warning: Exercise Makes You Fat", and "Why Doesn't Exercise Lead to Weight Loss?" The study that provoked the latter was published recently in The British Journal of Sports Medicine. Researchers from the Queensland University of Technology studied 58 obese people, who completed 12 weeks of supervised aerobic training without changing their diets.
Almost half of the participants failed to attain the predicted weight loss estimated from their exercised-induced energy expenditure – in other words, they didn't lose nearly as much weight as the research team had expected.
Another study, by scientists at the University of Colorado School of Medicine, Denver, recruited several groups of people: some lean endurance athletes; some who were sedentary but lean; some who were sedentary and obese. Each spent several 24-hour periods in a walk-in "calorimeter" (a special laboratory room that measures the calories a person burns). Each subject spent 24 quiet hours in the calorimeter, followed by 24 hours that included an hour-long bout of stationary cycling. To their surprise, the researchers found that none of the groups experienced "afterburn" – when your metabolism, raised through exercise, continues burning fat after the exercise has ceased. Crucially, the subjects did not use up additional body fat on the day they exercised. "The message of our work is really simple," says Edward Melanson, lead author of the study. "It all comes down to energy balance. It's not that exercise doesn't burn fat – it's just that we replace the calories."
He points out that a typical exercise session only burns 200-300 calories, which we replace with one sports drink. So is there any point exercising, or should we all just give up? If exercising doesn't lead to weight loss, is it time to bin the trainers and embrace a life of sloth? Of course not. The key here is to look behind the sensationalist headlines and grasp what the research is really telling us. For starters, we need to understand the difference that low- and high-intensity exercise have on the body.
Dan Carey, assistant professor of exercise physiology at the University of St Thomas in Minnesota, has published formulas detailing the heart rates at which a person could maximise fat-burning. "While there is a fat-burning zone in which there is a peak in the percentage of calories burned as fat, this intensity is relatively low," he explains. "The fat-burning zone heart rate usually lies between 60 and 80 per cent of maximum heart rate." So, rather counter- intuitively, we burn more body fat during lower-intensity exercise, but more calories with a higher-intensity workout.
Even though we burn more fat during lower- intensity exercise, to lose overall body weight we need to expend more calories, which means working harder.
The other key point here is that the Queensland University study did not include any dietary change for its subjects. They just exercised more. (They also experienced a wide range of non-weight-loss-related physical and mental benefits. The fact that this was woefully under-reported, and that their research has been so twisted by the press, has so incensed the team that they refused to comment for this story.)
"Are we really surprised that no changes to diet would lead to no change in body weight?" asks personal trainer Dax Moy. "Nutrition, as everyone knows, is the number one factor in controlling weight. Nutritional change alongside higher-intensity exercise training is the proven way to improve body composition, manage body weight and improve other health measures."
Also crucial is the point that muscle burns more calories than fat. For long-term weight loss, you need to change the composition of your body.
If you want to lose weight you have to combine exercise with dietary measures, says Roxy King, manager of LA Fitness in Holborn, central London. "If you just go on a diet, you will lose body fat but muscle percentage as well, and reduce your metabolic rate – which you don't want." For sustained weight loss, King and Moy recommend a combination of high-intensity cardiovascular exercise such as circuit training or spinning, with resistance training such as weight-lifting to build muscle mass.
"You need to maintain a higher metabolic rate so you're burning more calories on a daily basis. The only way to do that is with a higher percentage of muscle, which you will only achieve through exercise," says King.
Another common misconception is that an hour spent on the treadmill and exercise bike justifies an evening spent munching burgers and quaffing lager. As Jeni Pearce, performance nutritionist at the English Institute of Sport, explains, we often over- estimate the amount of energy we expend through exercise. "People may think they've expended 500 calories because they've worked really hard on the treadmill for an hour. But the reality is they may have only burned 250-300. Then they feel justified in eating a big meal and end up consuming far more calories than they've in fact burned."
One reason for this discrepancy is the difficulty in accurately measuring calorie expenditure. The key here is that the fitter you get, the harder you can work, hence the more calories you will burn during a gym session. Again, no excuse for burning the sports bra. Pearce is more used to working with elite athletes than the flabby masses, but does she have a final tip for us lesser mortals? "If you want to lose weight and keep it off the key thing is consistency," she says sternly. "To reduce body fat, or what I would call 'undesirable mass', takes time. It's a lot more difficult and takes longer than most people realise. You have to be in it for the long haul."
So there you have it. Despite our ever-more sophisticated understanding of how the human body works, and behind the screaming headlines, is a simple, commonsense message: losing weight requires time, effort and the right combination of exercise and diet. So put that cheeseburger down, lace up those trainers and hit the streets. Oh, and don't forget that you'll live longer and feel happier too.
Exercise and weight: Where we go wrong
* Giving up too soon It's tempting to give up on a healthy diet if you succumb to a calorie binge, or to let an exercise regime lapse if you're too busy and stressed to hit the gym. But renewing your commitment after a lapse is one of the most important things you can do. No matter how long it has been since you exercised, do something active right away – like going on a quick walk – to help you take control.
* Having the wrong attitude It's easy to view exercise as punishment – a necessary evil to balance out dietary lapses. No one enjoys punishment, so reframing your workouts is key. Remember that the human body is built for, and so craves, activity. Start thinking of exercise as your reward for a day spent hunched over your PC, and remember how good you'll feel when those cardio-induced endorphins kick in.
* Expecting immediate weight loss After weeks of exercising and sensible eating, it can be maddening when the scales won't budge. But you didn't gain that weight overnight, so it will take time to shift. Focus on the immediate benefits of exercise, such as increased strength, energy, alertness, improved sleep and a more positive outlook instead. Keep at it and the weight will shift eventually.
* Having unrealistic expectations We all dream of six-packs, sculpted thighs and rippling torsos, but, unless we won the genetic lottery, few of us can achieve them without Olympic-level training. So set yourself realistic goals, such as getting stronger or more flexible, banishing back pain through stronger abdominals and core muscles, or improving your posture, body image and self-esteem.
* Doing the same thing yet expecting different results It's all too easy to fall into a pattern with exercising where we do carbon-copy workouts every time we hit the gym. But muscles adapt extremely quickly, so to replace fat with lean muscle mass you have to keep shocking your body: ask gym staff for new exercises, try out different machines, and make sure that you cross-train – with a shifting pattern of weight-training, cardio-work, sports, swimming, cycling and running.
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