Cutting the fat between young adulthood and midlife can half your risk of a premature death, a new study shows.
Reductions in body mass index (BMI) approximately between the ages of 25 and 40 is critical to living a long life, US researchers said.
People whose BMIs went from the 'obese' range in early adulthood down to less than 'seriously overweight' in midlife cut the risk of dying by 54 per cent, they report.
Weight loss after middle age does not significantly reduce the risk of death, however, showing people are best advised to combat fat in midlife at the very latest.
Changes in weight between young adulthood and midlife may have important consequences for a person's risk of early death
Carrying extra fat can lead to cardiovascular disease, cancer, diabetes and even dementia in later life.
Around one eighth of early deaths in the US may be attributable to a higher BMI at any point between early- and mid-adulthood.
While in England, the number of obese people has almost doubled in the last 20 years from 6.9 million to 13 million, according to Diabetes UK – around 29 per cent of total English adults.
'The results indicate an important opportunity to improve population health through primary and secondary prevention of obesity, particularly at younger ages,' said study author Dr Andrew Stokes, assistant professor of global health at Boston University School of Public Health in the US.
WHAT IS BODY MASS INDEX (BMI)?
Body mass index (BMI) is a measure of body fat based on your weight in relation to your height.
The researchers used data from 1998 to 2015 for 24,205 participants from the National Health and Nutrition Examination Survey.
Also known as NHNES, the program is designed to assess the health and nutritional status of adults and children in the US across generations through interviews and physical assessments.
Participants were between 40 and 74 years old when they entered the study, at which point they had their BMI taken.
All participants selected for the study had also had their BMI taken at the age of 25.
Researchers then analysed the link between BMI change and the likelihood that a participant died over the course of the observed period, controlling for other factors such as their sex, education level and whether or not they smoked.
They found that participants whose BMIs went from the 'obese' range at age 25 down to the 'overweight' range in midlife were 54 per cent less likely to have died than participants whose BMIs stayed in the 'obese' range.
These participants who went from 'obese' to 'overweight' had a risk of death closer to that of participants whose BMIs had been in the 'overweight' range all along.
Lowest death rates were among individuals whose BMI stayed within the normal or 'healthy' range, which is deemed to be between 18.5 and 24.9.
The researchers estimated that 3.2 per cent of deaths in the study would have been avoided if everyone with a BMI in the 'obese' range at age 25 had been able to bring their BMIs down to the 'overweight' range by midlife.
In England, the number of obese people has almost doubled in the last 20 years from 6.9 million to 13 million, Diabetes UK reported late last year
However, weight loss was rare overall – only 0.8 per cent of participants had BMIs that went from the 'obese' to the 'overweight' range.
No significant reduction in risk of death for participants who lost weight in old age may be because weight loss during this time is more likely to be tied to an ageing person's worsening health.
Although leaving it until middle age to start losing some substantial weight is not advisable, the study does give some hope that it's not past all hope as we approach midlife.
The team didn't find a set age at which middle age kicks in, but just a general trend in terms of earlier versus later adulthood.
The study participants were defined as at 'midlife' mainly between the ages of 37 and 55, but 44 on average.
The research team believe it's more beneficial to lose weight in the earlier part of adulthood versus the later part of adulthood.
'Although this study focused on preventing premature deaths, maintaining a healthy weight will also reduce the burden of many chronic diseases such as hypertension, diabetes, heart disease, and even cancer,' said study co-author Dr JoAnn Manson, professor of medicine at Harvard Medical School.
WHAT IS OBESITY?ADULTS WITH A BMI OVER 30 ARE SEEN AS OBESE
Obesity is defined as an adult having a BMI of 30 or over.
A healthy person's BMI - calculated by dividing weight in kg by height in metres, and the answer by the height again - is between 18.5 and 24.9.
Among children, obesity is defined as being in the 95th percentile.
Percentiles compare youngsters to others their same age.
For example, if a three-month-old is in the 40th percentile for weight, that means that 40 per cent of three-month-olds weigh the same or less than that baby.
Around 58 per cent of women and 68 per cent of men in the UK are overweight or obese.
The condition costs the NHS around £6.1billion, out of its approximate £124.7 billion budget, every year.
This is due to obesity increasing a person's risk of a number of life-threatening conditions.
Such conditions include type 2 diabetes, which can cause kidney disease, blindness and even limb amputations.
Research suggests that at least one in six hospital beds in the UK are taken up by a diabetes patient.
Obesity also raises the risk of heart disease, which kills 315,000 people every year in the UK - making it the number one cause of death.
Carrying dangerous amounts of weight has also been linked to 12 different cancers.
This includes breast, which affects one in eight women at some point in their lives.
Among children, research suggests that 70 per cent of obese youngsters have high blood pressure or raised cholesterol, which puts them at risk of heart disease.
Obese children are also significantly more likely to become obese adults.
And if children are overweight, their obesity in adulthood is often more severe.
As many as one in five children start school in the UK being overweight or obese, which rises to one in three by the time they turn 10.