Two and a half hours of physical exercise per week may be essential for achieving any significant reduction in body weight, a new review of studies has found.

The review, published in the journal JAMA Network Open on Thursday, analysed previously conducted clinical trials probing the effect of exercise on weight loss.

It found that doing about 30 minutes of exercise a week was linked to only a modest reduction in body weight, body fat measures, and waist circumference among adults with obesity.

However, aerobic exercise exceeding 150 minutes per week, at moderate intensity or greater, was more likely to achieve clinically important reductions in weight-loss parameters.

Aerobic exercise is any type of physical activity that raises a person’s heart rate and gets them moving and sweating for a sustained period of time.

Previous studies have shown this type of cardio exercise provides a range of benefits when coupled with a healthy diet, enabling people to think more clearly, and even protect against cognitive decline with age.

Some previous studies have estimated the optimal minimum period of exercise at between 30 and 45 minutes.

As little as 30 minutes of aerobic exercise has been linked to significantly better performance on cognitive quizzes.

One study showed that about 30 minutes of treadmill walking for 10 consecutive days may significantly reduce depression.

But the exact amount of optimal exercise needed for weight loss has been unclear.

Health guidelines suggest that at least 150 minutes a week of aerobic exercise at moderate intensity is key to achieving meaningful weight loss of about 2 to 3kg. Some studies suggest a moderate intensity physical activity of about 225 to 420 minutes per week is required for weight loss of 5 to 7.5 kg.

The new study assessed data from over 100 clinical trials examining the effect of exercise over a duration of at least eight weeks on overweight or obese adults.

Researchers found that 30 minutes of aerobic exercise per week may enable adults who are overweight or have obesity to “slightly reduce” body weight.

However, they found the “greatest, clinically important” improvement from aerobic exercise of over 150 minutes per week.

“Aerobic training at least 150 minutes per week may be needed to achieve important reductions in waist circumference and body fat,” they said in the review.

“Longer durations of aerobic exercise may be associated with more beneficial weight or waist circumference outcomes.”

A decline in health and fitness isn’t inevitable once you cross into your seventies. Just take look at the recent snaps of Pierce Brosnan — age 70 — shirt off in the wilds of Yellowstone National Park. Or think of Angela Rippon, 79, high-kicking it on Strictly; Helen Mirren, 78, on the red carpet; or the verve of Bruce Springsteen, playing a three-hour set in Hyde Park, London, in the summer at the age of 73. These are just four examples of a host of septuagenarians and octogenarians who have demonstrated that vitality is possible at any age — if you’re prepared to work for it.

Skeletal muscle mass and strength decline more rapidly as we age and can affect physical performance, but this