The myth of the middle-aged spread

I plead guilty as charged m’lud. For the last four decades I have been telling patients who have been losing the battle with waistline spread that it’s their body's metabolism causing all the problems. This was conventionally believed to start to steadily slow year on year from the mid-30s onwards, meaning it became trickier to shift those stubborn pounds as time went by. It was also assumed that hormonal changes such as occur in pregnancy or the menopause further impacted on how quickly we burnt off calories, all adding to the struggle to keep weight off.

Well, it now seems that, along with the rest of my medical colleagues, I was probably doing those patients a disservice. A landmark international study just published in the journal Science looked at more than 6,000 people from 29 countries over 40 years and found that our metabolism peaks around the age of one, when babies burn calories 50 per cent faster than adults. It then gradually declines at a rate of roughly 3 per cent a year until the age of 20 and from there, rather than slowly declining as previously thought, it flattens out until about the age of 60. After this age it then starts to slowly decline again by about 1 per cent each year, which means that by the time we get to ninety our metabolism is running over a quarter lower than in it was in mid-life.

It only takes a quick glance down any high street in the country to see that being overweight or obese is now commonplace, which raises the question ‘If a slowing metabolism is not to blame for us getting heavier as we get older then what is?’

The obvious answer here is that the UK obesity epidemic is being fuelled by excessive food intake – we’re simply eating too much. This is further supported by the study finding that there appeared to be very little difference in total energy expenditure between early adult life and middle age which is when many people start to put on excess weight. Reduced energy expenditure as we get older certainly has an impact on potential weight gain but it now seems that it is excessive calorie intake driving weight gain rather than having a slowing body metabolism.

If these study findings are confirmed with subsequent investigations (and the data is unprecedented), this has important implications for both public health and the diseases of old age. If middle age, pregnancy, and the menopause don’t change our ability to burn calories it means that calorie restriction and regular physical activity are even more crucial in preventing weight gain than we previously thought — we can no longer say it’s harder to lose weight as we get older because ‘we’re not burning as many calories as used to’. It is also almost certainly not a coincidence that we start to see the impact of common diseases rising after our metabolism starts to decline again in older age. This may also have an impact on how our bodies metabolize drugs, and even how quickly cancerous cell changes may occur in some people.

Even with this change in message we now have to give to people, the fundamentals of weight loss remain familiar. Putting more calories into your body than you use up will cause a net gain in weight, with the type of food we eat heavily impacting on this. Eat healthily and exercise each day is the mantra.

Having recently turned 60, it would appear that now might be a good time for me to upgrade my treadmill.