Preventing the transition from pre-diabetes to type 2 diabetes is a major challenge in many countries. While several successful lifestyle interventions have been completed, much more insight into the composition of an optimal preventive diet is needed.
Now, following World Diabetes Day, the PREVIEW Project (PREVention of diabetes through lifestyle Intervention and population studies in Europe and around the World) has announced its main findings.
The PREVIEW intervention study compared a high-protein low-glycemic index diet to a conventional moderate-protein-moderate-GI diet for diabetes prevention and weight maintenance in people at risk of type 2 diabetes. The effect of combining either diet with high-intensity or moderate-intensity physical activity was also investigated.
Co-author and Professor of Human Nutrition at the University of Sydney's Charles Perkins Centre Jennie Brand-Miller, said the study was ambitious - and had yielded very hopeful results for people who are predisposed to developing type 2 diabetes.
"Overwhelmingly, participants who lost eight percent or more of their body weight in eight weeks and went on to complete the trial, did not develop diabetes within three years despite regaining some weight," said Professor Brand-Miller, from the School of Life and Environmental Sciences in the Faculty of Science.
Study participant Bruce Carr, before and after.
About the study
The three-year multi-centre randomised controlled trial was conducted in eight countries (Denmark, Finland, the Netherlands, the UK, Spain, Bulgaria, Australia and New Zealand), starting with an eight-week weight reduction phase, followed by a three-year weight maintenance phase.
In the first phase, participants had to achieve a weight loss of eight percent or more using total meal replacements. In total 2,326 overweight or obese adults aged 25-70 years with pre-diabetes were enrolled.
Ninety seven percent of trial graduates who had achieved the required fast weight loss had not developed diabetes by the end of the three-year trial.
Professor Brand-Miller highlights: "The most important finding in PREVIEW was the low incidence of diabetes in all groups at the end of the study."
Just 62 participants developed type 2 diabetes, giving a cumulative incidence of only one per 100 person-years. This compared with about five per 100 person-years in the diet arm of a 2002 Diabetes Prevention Study in the United States. In that study, participants had slower weight loss over a longer timeframe.
In the PREVIEW study, no differences were found between the two diets or the two physical activity programs, although fewer participants in the high protein groups achieved normal glucose status. With such a low incidence of diabetes, the researchers did not have the ability to detect any difference between the diet or physical activity arms. It is also important to note they did not have an untreated control group.
Next steps
Professor Brand-Miller said while promising, further work was needed to confirm the rapid weight loss in phase one was the main contributor to the study results.
"While it was a challenge for our participants to maintain the target protein and GI over three years, the combination of fast weight loss, healthy eating, behaviour change and physical activity seems to be very powerful," Professor Brand-Miller concluded.
"We believe this approach has been more successful in reducing the risk of type 2 diabetes than any previous diabetes prevention study and represents a significant clinical advance in the treatment of pre-diabetes."
The main findings of PREVIEW were published in November 2020 in Diabetes, Obesity and Metabolism.
Declaration: Professor Brand-Miller is the president of the Glycemic Index Foundation, oversees a glycemic index testing service at the University of Sydney and is a co-author of books about diet and diabetes. The lead authors have variously received honorariums from Novo Nordisk A/S, the International Sweeteners Association, Nordic Sugar, Unilever, and received travel grants from the Cambridge Weight Plan, which also donated the meal replacements. Refer to the published paper for full details.
