Q What is it about getting older? I’m sure my metabolism has halved since I turned 40. I’m 45 now. Can that be possible? Why is it harder to keep the weight off every year and why do I have so little energy? Is it an age thing? And before you give me grief, I am exercising. I do Zumba classes twice a week and I walk the dog every day – it’s a long walk and definitely counts as proper exercise so don’t go telling me it doesn’t. Anon

A I think every woman in her 40s reading this will identify with what you are saying. I know I do. In fact, this came home to me last week as the 40-year-old bridesmaid at my 29-year-old sister’s wedding.

Other than the obvious – that I looked haggard and ancient in comparison to everybody else, except my own mother – I was struck by how much more energy my sister and the other bridesmaids had for everything. The partying and carousing; the swimming; the dancing; the runs, not to mention how much food and drink they were able to consume. I must confess that I have never felt my age more acutely.

My sister insisted we went running on her wedding day, as she had done with me on my wedding day six years previously. The only difference – other than my age – was that we were doing it in 35 degree tropical heat in the Sri Lankan jungle.

It nearly killed me, but I swear she could have gone on for another hour. How did this happen? When did the gap between our respective fitness get so wide? After all, I’m still putting in the miles aren’t I? Has my metabolism really slowed down and is there anything we can do to boost these flagging energy levels?

Yes. We. Can. Women’s bodies are complex biological systems, and a combination of stress along with hormonal and metabolic changes, that really kick in after 40, mean we have to shift our eating and exercise habits to accommodate them.

One of the key changes, as you have identified in your question, is to our metabolisms. Our metabolism declines at the rate of at least 5 per cent per decade of life, starting at the age of 20 due to the natural loss of muscle mass.

Less muscle, few calories Dr Pamela Peeke, author of Fight Fat Over 40, spent three years investigating your question and puts a lot of it down to stress. In simple terms, as soon as we turn 40, our ability to burn calories drops and our stress levels soar.

The impact of these changes means we need to consume less food but, of course, as cruel nature would have it, we are beset with hormonal-induced cravings for sugary junk. So, what can we do about it?

Well, the really key things to watch remain the same. A crap-cutting approach to our diets is absolutely key; the difference being that our bodies are going to cling to that crap, because we no longer have the muscle mass to burn it off. So we have to be ever more vigilant.

We are knackered and stressed, and it is not just hormones, but the everyday reality of our lives: all of our responsibilities seem to reach a peak during this decade.

If you have children, they are most likely still at home and you may be caring for ageing parents as well. Not to mention possibly coping with partners, who may be driving us up the wall, and full-on jobs to boot.

Overeating in the late afternoon and evening is one of the biggest culprits behind stress-induced weight gain in women over 40.

What happens is that later in the afternoon, the stress hormone cortisol plummets and intense fatigue sets in, so the temptation to eat crap and guzzle caffeine in the hope of giving ourselves an energy boost can be overwhelming.

Peeke recommends consuming about 60 per cent of your day’s calories by 6pm. I reckon if you try to live by the maxim, breakfast like a king, lunch like a prince and dine like a pauper, you won’t go far wrong.

Sadly, stress eating will do exactly what it says on the tin . . . generate more stress. So, stick to foods that don’t stress the body, the obvious healthy stuff: wholegrains, skimmed milk, vegetables, fruit and oily fish, and you will be combating stress levels as opposed to ramping them up.

Developing a positive habit around consuming healthier foods is your ticket to maintaining greater resilience in the face of daily events which would normally send you to the coffee maker and cake stand.

And, of course, that regular run or, in your case, long walk. Ramp it up, go on and treat yourself to some of those wrist weights I wrote about in a previous column. Ankle weights too if you are feeling pumped.

After all, you are walking anyway, these little add-ons will make your body work at least 15 per cent harder over every walk.

Try to mix up your daily routine to inject some physical activity into this afternoon period when we geriatrics are most at risk of a biscuit binge. Walking home from work would be an obvious solution. Or going for a walk or run or swim after you get back from work instead of hanging around the kitchen and the biscuit tin.