Diet plays an important role in health, and in the development – or otherwise – of many diseases. This association is all the more important at a time when excess weight and obesity are steadily on the rise in certain regions, including Europe, where almost two-thirds of adults and one-third of children are overweight or obese, according to the World Health Organization.
The scale of the phenomenon is such that scientists are increasingly interested in the properties of foods, whatever they may be, to prioritise those that can be more beneficial to health.
This is the subject of a vast study that looked specifically at the role of carbohydrates in weight gain and obesity over the very long term. The researchers used data from 136,432 men and women aged 65 and under who participated in various studies, over a follow-up period of 24 years.
These men and women were in good health at the time of enrolment, and were asked to complete several questionnaires on various criteria, such as medical history or lifestyle, at the start of the research and then every two to four years. The researchers observed an average weight gain of 1.5kg every four years – or almost 9kg over the study period.
Among the main findings, published in the British Medical Journal (BMJ), the researchers report that increases in glycemic index and glycemic load – in other words, the effects of particular foods on blood glucose levels – were associated with long-term weight gain.
They also suggest that increased consumption of carbohydrates from refined cereals, starchy vegetables (potatoes, corn, peas), and sweetened drinks was associated with greater weight gain around midlife than increased consumption of fibre and carbohydrates from whole grains and non-starchy fruits and vegetables.
In detail, they observed that an increase of 100g of starch or added sugar per day resulted in 1.5kg and 0.9kg more weight gain on average, respectively, over four years, while an increase of 10g per day of fibre was linked to 0.8kg less weight gain.
Looking at vegetables in particular, weight gain was lower with increased consumption of carbohydrates from broccoli, carrots and spinach, rather than carbohydrates from potatoes, peas and corn.
“The associations were stronger among participants with excessive body weight than those with normal weight,” the researchers summarised, adding that these associations were stronger in women than in men.
Despite the limitations of this observational study, which relies in particular on self-evaluation, the researchers emphasised it is “a large study using repeated dietary assessments and validated questionnaires over a long follow-up period, spanning the important period of weight gain in midlife”.
The findings “highlight the potential importance of carbohydrate quality and source for long-term weight management, especially for people with excessive body weight”, they added.