As midlife sets in, maintaining a healthy weight often becomes harder. Tricks that worked in the past, like cutting down on wine or sugar, no longer seem to work, either. Even slender Samantha Cameron, now 50, has apparently been affected. In her 30s and early 40s, staying in shape was easy, she said this weekend, “but then I hit 43, I just put on three-quarters of a stone. Suddenly you don’t quite fit any of your things and I got really bloated.” At first she tried doing the 5:2 diet – eating normally five days a week, then having just 500 calories on the other two – but “I just couldn’t do it, I literally couldn’t speak in the evening, I had to go to bed at 7pm.” She has recently found a solution: the 5:2 principles, but with 800 calories on the “fast” days, and says she’s “loving it” and “the bloating’s gone”. Alongside three weekly workouts, she says it’s helping to keep her trim: her goal is “to hit my 50s in almost as good shape as I hit my 40s.” If you’re struggling to maintain your weight and fitness post-50, here’s why – and what to do about it: Muscle mass Every decade after the age of 30, we on average lose three to eight per cent of our muscle mass. At first, this might not be noticeable, but by 50 or 60, will make a considerable difference. This is bad news if you want to lose weight, because muscle burns on average three times more calories than fat per day, even at rest. What to do: Incorporate resistance training into your weekly routine to reduce muscle loss. The NHS recommends two sessions of strength training a week, which could include activities as varied as gardening or lifting weights. Don’t underestimate the good that exercise can do: a 2018 study shows that regular exercisers over the age of 55 kept up their muscle mass considerably more than inactive people. Staying active In England, half of 16 to 24-year-olds are doing the recommended amount of weekly exercise, but only one in 10 people aged 65 to 74 are doing so. If injuries have accrued, and your work and social life is less busy than it once was, you may be leading a more sedentary lifestyle than you realise. The role of exercise in weight loss is much-debated, but it can be crucial in maintaining your weight. A famous 2016 study followed participants in American weight loss competition The Biggest Loser during and after filming, and found that most regained a lot of weight after the cameras stopped rolling due to a higher appetite and slower metabolism. However, a follow-up study in 2017 found that the contestants who kept the most weight off were those who had remained committed to a fitness regimen. This was particularly interesting given that more exercise didn’t equal more weight loss during the show, when those who lost the most focused on diet over working out. What to do: Try to stick to the NHS guidelines on exercise, which recommend 150 minutes of moderate exercise a week, or 75 minutes of vigorous exercise, or a mixture of both. Make sure you are doing something appropriate for your body, too. As we get older, high-impact workouts like running may place unwanted stress on your joints, so think about lower impact options like swimming or cycling. Hormones Menopause changes where fat is stored on the body. Higher oestrogen levels in the fertile years cause fat to be stored on your legs, hips and behind, but after oestrogen drops, fat can move to your middle, even if you remain exactly the same weight. This can be an issue, as fat around your trunk is more likely to contribute to Type 2 diabetes, hypertension and heart issues than fat on your hips and legs. Men are affected by hormone changes as they age, too: after the age of 40 they lose roughly one per cent of their testosterone a year. This matters for weight, as testosterone is linked to the amount of muscle you have and where you store fat. What to do: For women, several studies suggest that HRT can help to stop the shift of fat from your bottom half to around your middle as you go through menopause. An Italian study followed two groups of equal weight post-menopausal women for a year, putting half of them on HRT, with the rest going hormone-free. At the end of the year, the HRT group stayed almost the same weight, and hadn’t put on any extra fat around their middles or arms. In the untreated group, things were different: they had put on three and a half pounds, and had increased the amount of fat around their waists and arms. HRT isn’t suitable for everyone, so make sure you consider your options and discuss with your doctor first. In men, hormones are linked to a variety of lifestyle factors, including body fat and waist size, which can increase the amount of oestrogen in your body. Keeping active is also vital for men’s hormones: a 2018 study found that regular cyclists aged 55 to 74 kept their testosterone levels up compared with inactive men. Your sleep is also a partial predictor of your testosterone levels: most of the hormone is released while we doze, so if you’re not getting enough hours in bed, your body has less chance of boosting its stores. Getting enough sleep is key for maintaining your weight for other reasons, too: not getting enough is shown to make you gravitate towards sweet foods, and muscle growth occurs largely while we’re resting at night. More stress For many, juggling looking after children and caring for parents with work can mean life post-50 requires navigating a huge amount of stress. Even if you eat exactly as you did before, stress can cause weight gain. In 2015, American researchers found that after eating a large meal, women who reported more stress in the previous day burned 104 fewer calories than women who weren’t stressed. Stressed women also had higher levels of insulin, which is linked to gaining fat. This may not sound significant, but burning 100 fewer calories a day could lead to a loss of 10lbs of fat over a year. What to do: Reducing stress is often one of the hardest lifestyle changes to make, as you may have little control over the issues at work or home. However, you can change how you react, which can reduce your stress levels even without anything changing in your external environment. Exercise is an incredibly effective way of lowering cortisol levels, as well as burning calories, which could lead to a double effect on your weight. There is also robust evidence that simply slowing your breathing can dramatically reduce stress in both the short and long term, as well as giving a range of other benefits like better sleep. “Slow” counts as anything less than 10 breaths a minute, and six breaths is even better. The NHS recommends inhaling for up to a count of five, then exhaling for the same length of time.