With the latest NHS England data revealing that two-thirds (66%) of adults in England either overweight or living with obesity, experts are urging people to look beyond BMI alone when assessing their long-term health.
The data also found that seven in 10 (70%) adults had a waist-to-height ratio above the recommended level of 0.5, meaning they had higher levels of abdominal fat.
At the same time, biological age has become an increasingly visible topic in health and wellness conversations. Weight loss experts at Tonic say the growing interest reflects a wider shift in how people think about health, moving beyond what they weigh and towards how well their body is functioning internally.
Unlike chronological age, which is simply the number of years a person has lived, biological age is used to describe how well the body appears to be ageing on the inside. It can be influenced by factors such as weight, waist size, fitness, muscle mass, blood sugar, sleep, lifestyle and wider metabolic health.
In simple terms, someone’s biological age may be higher or lower than their actual age depending on how well their body is functioning.
Jordan Chadwick, Director at Tonic, says the comparison between BMI and biological age shows why health should not be reduced to a single number: “BMI can still be useful as a quick screening tool, but the problem comes when people treat it as a complete verdict on their health. It was never designed to explain the full picture, and on its own it can miss some of the most important details.
“Two people can have the same BMI and be in very different places health-wise. One person may have more muscle, better fitness and stable blood sugar, while another may be carrying more weight around the waist and have a higher level of metabolic risk. That is why looking only at height and weight can be too blunt.” Jordan tells us.
Because BMI screening tools cannot tell the difference between muscle and fat, or show where fat is carried, Jordan says people should treat BMI as one part of the picture and focus on habits that support healthier ageing over time.
6 Ways to slow your biological clock
1. Don’t just watch the scales, watch your waist – BMI doesn’t tell the whole story when it comes to health. NHS England found that 70% of adults had a waist-to-height ratio above the recommended level, highlighting the importance of looking beyond weight alone. Because abdominal fat is more closely associated with metabolic risk, keeping an eye on waist health could provide another useful indicator of long-term health.
Jordan said: “A healthier weight can reduce strain on the body, but the route matters. If someone loses weight in a way that is too restrictive or unsupported, they may struggle to keep it off. Sustainable change usually comes from a plan that protects nutrition, supports movement and fits real life.”
2. Treat muscle as your ‘anti-ageing’ insurance policy – The number on the scales can’t distinguish between fat and muscle, while BMI doesn’t reveal how well the body is functioning metabolically. Maintaining muscle is particularly important for strength, mobility and metabolism as we age, while elevated glucose has also been associated with faster biological ageing when measured using epigenetic tools.
“Muscle is central to the bigger health picture. It supports strength, mobility and metabolism, which become increasingly important as we age,” She added. “If we only look at BMI, we miss the things that tell us how well the body is coping day to day.”
3. Your daily movement matters more than one trip to the gym – Physical activity isn’t just about burning calories, it can help slow biological ageing, while higher BMI, elevated glucose and poorer blood pressure profiles have been associated with faster ageing when measured using epigenetic tools.
Building movement into everyday life, from walking and taking the stairs to breaking up long periods of sitting, can help support health over the long term.
“Movement should not be framed only to burn calories. Regular activity helps improve insulin sensitivity, cardiovascular fitness, strength and mood, all of which influence how well the body functions over time. Even small increases in movement can make the wider plan easier to maintain.”
4. Don’t wait until you age to think about blood sugar – Elevated glucose has been associated with faster biological ageing in research using epigenetic measures, suggesting that blood sugar regulation isn’t simply something to worry about later in life. Regular movement, maintaining muscle and eating a balanced diet can all support better metabolic health.
“Maintaining steady blood sugar levels is vital for metabolic health. Blood sugar can affect energy, hunger, cravings and long-term metabolic risk, so it’s worth paying attention to at every stage of life rather than treating it as something to worry about later.”
5. Make sleep part of your health plan, not an afterthought – Sleep is often treated as a luxury rather than part of a health routine, but it plays a role in appetite regulation, mood, recovery, energy and resilience. For anyone trying to improve their health, consistently poor sleep can make it harder to maintain healthy habits.
“Sleep is one of the first things people sacrifice, but it underpins appetite, mood, recovery and decision-making. If someone is exhausted, it becomes much harder to move regularly, plan meals and make consistent choices,” Jordan explained. “Poor sleep can quietly undermine the whole process.”
6. Don’t let your desire for a younger body age your mind – The pursuit of better health can become counterproductive if it creates constant pressure around weight, food or appearance. Sustainable health changes need to work psychologically as well as physically, with support and realistic expectations playing an important role.
“The mental side of weight loss is just as important as the physical side. If people feel ashamed, rushed or constantly judged by numbers, they are less likely to build habits that last. The aim should be support, structure and confidence, not pressure.”
Jordan said that while the growing focus on biological age is encouraging people to take their health more seriously, it should not become another number to obsess over: “Losing weight is never just about making the number on the scale smaller. The real question is whether the body is becoming healthier as a result,” she said.
“That is why quick fixes can be so misleading. Someone can lose weight quickly but still feel exhausted, unsupported and unable to maintain the change. A healthier approach looks at what is happening underneath: metabolism, movement, nutrition, sleep and the mental side of weight loss.”
Indiana Lee lives in the North West and has a passion for the environment and wellness. Indiana loves experiencing new things and sharing with others what she learns through her writing. You can chat with Indiana on twitter @IndianaLee3
