A new three-decade study led by researchers at St. George’s University of London showed that obese young people can still avoid type 2 diabetes and other complications if they change their habits before middle age.

The study was published in the journal BMJ Open and is entitled “Body mass index in early and middle adult life: prospective associations with myocardial infarction, stroke and diabetes over a 30-year period: the British Regional Heart Study.”

While the body’s adiposity — fat stored in fat tissue — in middle age is considered a risk factor for type 2 diabetes and cardiovascular disease, its impact on early adult life is not clear. Researchers in England have now investigated the effects of high body mass index (BMI) in early and middle adulthood on the risks of developing type 2 diabetes, stroke, and myocardial infarction (MI) in later years.

The team collected data on the BMI of nearly 5,000 men at 21 years old through military records from the English military service, and later when they reached middle age (40–59 years). Researchers found that men who at a younger age had high BMI levels but were able to reduce them by the time they were 50 years old had a similar or even lower rate of type 2 diabetes prevalence compared to men who  had a normal BMI at younger age.

Based on these results, Professor Christopher Owen, the study’s lead author, said that high BMI levels in early life does not necessarily mean someone will develop type 2 diabetes later in life, since the effects of high BMI may be reversible.

“Even in men who carried out UK National Service and were relatively thin in early life compared to more recent men, higher levels of fatness in early adult life appear to be associated with later diabetes,” Owen said in a news release. “However, effects of early body mass appear to be reversible by subsequent weight loss. These findings have important implications for type 2 diabetes prevention, especially in more recent adults with high levels of obesity.”

The authors concluded that a high BMI level earlier in life did not influence the risk of heart attack or stroke, but men who were obese at middle age had higher chances of heart attack, stroke, or developing type 2 diabetes. Researchers suggest that early obesity prevention is the key to reducing the risk of type 2 diabetes later in life. More than 4 million people in the UK are considered at high risk of developing the disease.