I do my 75 minutes’ of vigorous weekly exercise, and easily hit the Government target of two hours and 20 minutes of “brisk walking” (even if some of it is on the way to buy bagels). My arms, legs and shoulders are in pretty good nick. So why then am I left with a squishy tyre around my belly?

According to a significant new study, at the age of 53, I can no longer blame my metabolism for this unattractive middle-aged spread. The paper, from Aberdeen University and published in the journal Science, suggests that a person’s metabolism remains “rock solid” throughout midlife – and only starts to decline from the age of 60.

“It’s a picture we’ve never really seen before and there are a lot of surprises in it”, says Professor John Speakman, of the study which followed 6,400 people from just eight days old up to the age of 95. “The most surprising thing for me is there is no change throughout adulthood. If you are experiencing middle-life spread, you can no longer blame it on a declining metabolic rate.”

Metabolism is described as an organism’s set of life-sustaining chemical reactions, including the conversion of the energy in food to energy in a person’s body. The bigger one’s body (whether through fat, or muscle), the more energy it will take to run.

It’s been known for some time that exercise alone is not enough to lose weight. In his book Burn: The Misunderstood Science of Metabolism, out earlier this year, Herman Pontzer wrote: “We have got the science of energy expenditure fundamentally wrong. All the research we have been doing in the last 10 years… points to diet as being the culprit here for obesity. It’s not sloth, it’s the food.”

And what of the 10,000 Fitbit steps – a daily Holy Grail for many? A typical adult burns around 250 kcal while performing these, according to Pontzer. “This is roughly equivalent to half a Big Mac,” he says. “Climbing one set of stairs burns about 3.5 kcal – less energy than you’ll get for a single M&M. If you start a new exercise programme tomorrow and stick to it religiously, you will most likely weigh the same in two years as you do now.”

Before we get too despondent, it’s beyond dispute that physical exercise remains vital for protecting us against every major disease, for bone health, and maintaining weight loss. So what extra is needed to up our game to lose that belly fat as well?

Matt Roberts is a highly experienced personal trainer: his personal training gym, opened in 1996, was the first such establishment in Europe. For Roberts, the science is both correct and easy to misinterpret. “You can increase your metabolism by exercise, but not by dieting,” he says. He points to the after-effects of exercise as a potential for burning calories: “The after-burn is where the wins are.”

Roberts says there are several common reasons for mid-life weight-gain. “In our earlier lives, we were always challenging our system, maybe with team sports or simply being out on our bikes,” he says. “But as we approach middle age, there is a shift in attitude. We think: ‘Why not have a drink on a Tuesday night, if I’m going to gain weight anyway?’”

This view is compounded by stress in our daily lives – hence we turn to alcohol, tobacco and other substances which strain our body. “Our parasympathetic nervous system reacts, changing our hormones,” he says. “If we do burn energy, it’s more likely to be sugar than fat.” Visceral fat (the stuff around our middles) is the “bad one”, increasing the risk of heart disease, type two diabetes, strokes and even Alzheimer’s.

A lack of refreshing sleep also leads to a slowing of the metabolism plus a rise in cortisol and testosterone (and was the reason that this writer gained weight in her late 40s). “The key to midlife weight-loss is to maintain a healthy diet, to sleep well, and to do the right sort of exercise,” says Roberts. Here are some of his tips:

 

1) Perform Zone Two training for 45 minutes, four days a week

“By this, I mean moderate cardiovascular exercise, where your heart-rate is at 65 to 70 per cent of the maximum,” says Roberts. “A fast walk, or slow run, where you are out of breath when you try to talk. Do this consistently several times a week, and it’s a slow but sure way to burn fat.”

2) Lift something heavy two to three days a week

Ideally in a gym. “Lifting is better than pushing,” says Roberts. “Try a leg press, as heavy as you can manage: do six or seven reps, then rest.” This will help your muscles grow in strength, not mass. He also points to the importance of building bone density to prevent osteoporosis, particularly important for midlife women.

3) Do short bursts of high intensity training twice a week

“Push yourself for 20 to 25 seconds at a high level – on a bike, for example,” says Roberts. “Then rest for a minute to two and a half minutes, then repeat six to 10 times. Exercise is the trigger to demand your body to make more energy.”

4) If you can bear it, have an ice-cold shower for five minutes every morning

 “Research from Stamford University shows that giving your body a ‘DNA shock’ can have huge effects on the production of cortisol and serotonin, and can lead to weight loss,” says Roberts. “But this can be quite an undertaking.”

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