It is a simple question with a very complicated answer: how much should you weigh? While many people spend their 30s, 40s and 50s watching their weight, the evidence suggests that by the time you reach your 70s, you should be more preoccupied with maintaining – or even gaining – weight than losing it.
In mid-April, scientists from Monash University in Australia discovered that losing weight in old age could be a warning sign of early death. In a study of more than 16,000 healthy pensioners, published this week, elderly men who lost more than 10 per cent of their body weight were almost three times more likely to die in the next few years than those who didn’t.
For women, a 10 per cent loss in body mass more than doubled the risk of death. Those involved had no existing chronic illnesses at the start of the study and were assessed over the course of four and a half years.
No magic number
So, what is a healthy weight for your 40s, 50s, 60s and beyond? While it’s true that our body composition and energy needs change as we age, there is no magic number for each decade, provided your weight remains in a healthy range.
“The trajectory is that most people will get heavier with age until they reach their 60s, and then they begin to lose weight,” says Giles Yeo, professor of molecular neuroendocrinology at the University of Cambridge and the author of Why Calories Don’t Count.
But the “ideal” weight “depends entirely on who you are, because the amount of fat you can store safely is individualised”, he says. “There are going to be larger people who are metabolically fit and skinny people with diabetes.”
This is because when you lose or gain weight, the number of fat cells in your body doesn’t increase or decrease. Instead, says Professor Yeo, you should think of them “like balloons – the fat cells expand or shrink, and everyone’s fat cells expand differing amounts, meaning people store different amounts of fat safely. We need to know that for each individual – it’s trickier to measure than you might imagine, but that’s the goal.”
The problem with BMI
Until then, we rely on a cruder measurement: Body Mass Index (BMI). For decades, BMI – weight in kilograms divided by the square of height in metres – was considered the most accurate measurement for health.
Adults with a BMI of 18.5-24.9 are considered to be a healthy weight, regardless of age, according to the NHS. While BMI remains a useful metric, it’s no longer considered quite so clear-cut.
“The major problem with BMI is that it doesn’t take into account the amount of fat or muscle you have,” Yeo says.
“Tracking BMI across a population is useful: on average, the higher your BMI, the more fat you carry, and the more unhealthy you’re likely to be. But on an individual basis, it’s not the best measure: if you’re a doctor looking at the human being in front of you, you need to look at how healthy the individual is. Are they young, muscular, older, have they just had a baby?”
Healthy waist-to-height ratio
More recently, experts have emphasised the importance of a healthy waist-to-height ratio. This is determined by dividing waist size by height: both men and women should keep their waist circumference at no more than half their height. “Where you put your fat also influences how healthy you are,” says Professor Yeo.
Extra inches around the middle are more dangerous than an increase in overall weight, as visceral fat accumulates around internal organs and is linked to an increased risk of cardiovascular disease and cancer. This explains why someone “pear-shaped” could be healthier than someone with an “apple” body shape, even if they weigh more.
Obesity (a BMI of 30 or above) raises the risk of many health conditions, such as stroke, heart disease, type 2 diabetes and some types of cancer. Thirty per cent of the UK population is obese. But in later life, being underweight (a BMI of under 18.5) is also linked to poorer health outcomes: it increases the risk of nutritional deficiencies, bone fractures and osteoporosis, and weakens the immune system.
Here’s what you should aim for in each decade.
40s and 50s
The time of “middle-age spread”. “People in middle age tend to be less active because we’re sitting on our backsides doing our jobs, plus the fact that we have more money, on average, and so eat richer foods,” Yeo says.
Good levels of physical activity will help counteract this: 30 minutes of moderate exercise a day should suffice (this includes brisk walking, hiking or riding a bike).
Provided your BMI is within the healthy range or thereabouts, you should focus on maintaining muscle mass and keeping your weight-to-height ratio healthy, rather than aiming for a specific number on the scales.
“The amount of muscle you are carrying is the most critical piece of information as you get older,” says Professor Yeo. “The more muscle you have as you get older, the healthier you’re going to be.”
Contrary to popular opinion, metabolism doesn’t immediately drop off a cliff in middle age, he says. “Your metabolism stays stable for a surprisingly long time – until 60 or so – before it begins to fall.
“You might say, hang on a second, why do we get middle-age spread in our 50s? That’s to do with the second part of this equation, which is muscle. When people get older, we’re not as physically active, and you begin to lose muscle,” he says.
“Muscle has the highest metabolic rate in your body, so you could be the same weight, but carrying more fat than muscle, and then the metabolic rate will lower.” Your basal metabolic rate is the number of calories your body burns simply by being alive.
Aim for the two sessions of strengthening activities or resistance training per week to address this: bodyweight exercises, such as push-ups, working with resistance bands and lifting weights (or, indeed, heavy shopping bags), all count towards this goal.
60s
A renewed focus on eating well is advisable in your 60s: keeping your weight within a healthy range will help combat a slowing metabolism.
If your weight creeps up, now’s the time to address it with a diet rich in protein and low in sugary, processed foods and refined carbohydrates, which include white bread, pasta, pastries and pies.
This diet switch can have remarkable benefits for overall health and longevity. In 2021, a major study from Johns Hopkins University found that, aged 60, switching from an “average” diet high in processed foods and red meat to a healthy one high in grains, legumes and nuts can add almost a decade to your life.
“In your 60s, it’s probably not too late to lose weight, as it enhances your ability to live healthier for longer,” Yeo says. Start by building up moderate aerobic exercise, such as brisk walking, until you reach the recommended 150 minutes per week.
“You might still be working towards retirement, so there is the opportunity to extend your life, and I think people need to think about that.”
70s and 80s
In your 70s and 80s, the focus should shift from losing weight to maintaining or gaining it: some studies suggest that a few extra pounds could even be beneficial in this age group. In America, the National Institutes of Health suggests that older adults should try to keep their BMI between 25-27, rather than the 18-24 range for younger people.
A study published in the Journal of Epidemiology and Community Health in 2012 found that in people aged 65 and over, all-cause mortality was lowest in those who had a BMI of 25-29.9 for men and 25-32.4 for women.
Another recent study from the Archives of Orthopaedic and Trauma Surgery found that older patients with a higher BMI had a significantly reduced mortality risk following surgery.
“As you go into your 70s and 80s, in particular, obesity is no longer a major problem because you lose weight quite rapidly,” says Professor Yeo, through a loss of muscle mass or appetite.
“It does tilt to a point where if you’ve survived to your mid-70s, does it really matter if you have butter on your toast? I think you should just live your life the way you want to live it.”
Strength training is more important than ever, as muscle helps maintain cardiovascular health and bone density. “No matter how old you are, you should always do resistance training,” Yeo says.
That doesn’t have to mean “pumping iron” – even the simplest strengthening exercises, such as chair sit-to-stands and calf raises, could make a difference in maintaining muscle mass.
“I think people underestimate how much that matters – and it really, really matters when you get older,” he says. And remember: it’s never too late to get fitter.