Dr Michael Mosley believes gruelling workouts are not the secret to winning the battle of the bulge. In fact, he says it’s one of many misleading weight-loss myths that can cause some people to struggle to slim.
Here, the renowned health journalist, who devised the popular 5:2 diet, explodes some of the most persistent fitness myths.
MYTH: Exercise is a good way to lose weight
Believe it or not, it’s not true that exercise, whether walking or jogging, is a good way to lose weight. It can be, but only if you push yourself.
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Dr Michael Mosley says that exercise as a weight-loss technique is a myth
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Dr Michael Mosley says that exercise as a weight-loss technique is a myth
The problem is that fat is extraordinarily energy-dense. Each pound of fat packs in about 3,500 calories. The average woman eats about 2,000 calories a day, so that represents nearly two days’ worth of food.
So how much exercise would you need to do to burn off 1 lb of fat?
Well, if you are a woman weighing 10 st then you will burn about 100 calories running a mile. This means you will have to run about 35 miles to get through 1 lb of fat. You could do it in one go, which would be tough and possibly dangerous, or run an hour a day at a reasonable pace of 6 mph for six days.
But even that doesn’t guarantee you will lose weight, as it assumes you won’t then compensate by eating more, which many people do.
A recent Australian study took 45 overweight young women and split them into two groups. One was asked to cycle at moderate intensity for 40 minutes, three times a week, for 15 weeks.
The other group did 20 minutes, three times a week, but alternated short, vigorous bursts (only eight seconds long) with gentle cycling. At the end of the trial, just as they had at the beginning, they had their body fat measured.
The group doing the short bursts of vigorous cycling had lost an average of 5 lb of fat, but the group doing the moderate cycling put on an average of 1 lb of fat.
The vigorous cycling probably worked better because of an after-burn effect, as high-intensity exercise revs up your metabolism and leads to the release of hormones like adrenaline, which burn fat. It may also be because vigorous exercise tends to suppress appetite.
If you want to lose weight you need to control your calories, increase your general activity and make sure the exercise you do is intense. Exercise alone is unlikely to be enough.
MYTH: Everyone gets fitter if they exercise
Before I met Professor Jamie Timmons at Loughborough University, I would have bet my bottom dollar that this statement was true. Now I know otherwise.
Professor Timmons checked how strong my heart and lungs were by measuring my VO2 Max, which is a measure of how much oxygen your body can consume when you’re pushing yourself. The fitter you are, the higher the figure.
Not everyone can get fitter by exercising
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Not everyone can get fitter by exercising
I then went away and did an intense exercise regime for several weeks. Yet when I repeated the VO2 Max, I got exactly the same score. I couldn’t believe it.
Professor Timmons explained there is a huge variation in how people respond to an exercise regime and there is no guarantee of favourable results.
This is backed up by the findings of a recent study in Finland. They asked 175 untrained, middle-aged men and women to do a 21-week fitness course.
The volunteers either did weight-lifting twice a week, endurance training twice a week or a workout that combined strength and endurance training four times a week.
The results were mixed to say the least. Some people’s fitness improved by an impressive 42 per cent, while others became less fit — their VO2 Max dropped by 8 per cent, a finding that had the researchers baffled.
There was an even greater spread when it came to the strength exercises, with some people increasing theirs by 87 per cent and others performing 12 per cent worse than at the beginning.
A number of studies have come up with similar findings.
As Professor Timmons points out, there is a huge range in people’s responses to exercise — from super-responders at one end of the spectrum, to non-responders at the other. There are almost certainly genetic reasons for this.
That said, exercise is always a good thing to do. While some people, like me, may not improve their aerobic fitness, they will benefit in other ways, such as the way they control their blood sugar.
MYTH: Exercise in the gym lifts your mood
This is a widely held belief, but is it true? People who do lots of exercise, particularly long-distance runners, report feeling happier and plenty of people get a real kick out of exercise.
The popular explanation for this is ‘endorphin release’. These are chemicals produced in response to stress.
The trouble is that while increased endorphin levels have been measured in the blood of some people after they exercise, it doesn’t happen in everyone and it is unlikely the endorphins being measured could have created the euphoric feeling anyway. Endorphin molecules are too large to cross the blood-brain barrier and reach the brain. So exercise may not be quite as effective a mood booster as it’s sometimes claimed to be.
The happy feeling we get while exercising is in fact due to the release of chemicals in response to stress
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The happy feeling we get while exercising is in fact due to the release of chemicals in response to stress
A 2012 study at Bristol University backs this up. It took 361 patients with depression and divided them into two groups. One group continued as normal, the other group doubled its exercise. At the end of a year, there was no evidence the exercise had improved their mood or led to less use of anti-depressants.
As Dr Melanie Chalder, from Bristol University’s School of Social and Community Medicine, acknowledged: ‘Our intervention was not an effective strategy for reducing symptoms.’
There is much more evidence to suggest just being outdoors in a green environment will have a positive impact on mood. Being in a natural setting is closer to how our remote ancestors would have lived. So remember, going for a run or walk in the park is more likely to cheer you up than doing the same exercise in a gym.
MYTH: If I work out, I can eat lots more
Thanks to our evolutionary past, when food was scarce and our ancestors were active, our bodies are incredibly efficient at doing things like walking or running. You have to do a lot of either to burn even a small amount of calories.
Working out doesn't mean you can eat more food without gaining weight
Working out doesn't mean you can eat more food without gaining weight
I researched how many calories I burn while running by wearing special monitoring equipment and set off at a brisk pace around the athletics track at Loughborough University. The equipment suggested I was burning about 16 calories a minute, which meant that having run just over a mile I had got through 160 calories.
However, a latte contains about 150 calories, while a chocolate muffin comes in at 500 calories. So if you decide to have a relatively small snack like a muffin and latte after your run, you are topping yourself up with 650 calories — far more than what you’ve burnt off.
And it gets worse. When you are judging the impact of going for a run, you should take into account the fact that you burn a lot of calories just sitting down and doing nothing.
In fact, most of the calories we burn are consumed keeping our bodies going. What you want to know is not the total calorie burn (TCB) but the net calorie burn (NCB), that is how many extra calories you burn by running rather than doing nothing.
To calculate your net calorie burn from running a mile at a reasonable pace i.e. doing 6 mph, or walking at about 3 mph, then use this formula:
Net calorie burn from running a mile at about 6 mph = 0.7 x your weight (in lb).
Net calorie burn for walking a mile at about 3 mph = 0.4 x your weight (in lb).
I weigh 168 lb, which means my net calorie burn from running a mile is about 117 calories.
So 117 calories a mile means I would have to run nearly six miles to burn off a muffin and latte. Or I could walk nine miles. Best to leave that muffin alone.
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