'Eat more flavonoid-rich fruits and veg to prevent weight gain
There are more than 6,000 types of flavonoids, which are naturally present in most fruits and vegetables. Some of the more well-known types include flavonols, flavones, flavanones and anthocyanins.
Previous studies have associated dietary flavonoids with weight loss, though the team involved in this latest study - including Monica L. Bertoia of the Harvard T.H. Chan School of Public Health in Boston, MA - notes that most research has focused on the weight-loss effect of flavan-3-ol, a flavonoid found in green tea.
What is more, Bertoia and colleagues say most previous studies assessing the link between dietary flavonoids and weight loss have only included a small number of participants who were overweight or obese.
For their study, the team set out to assess how intake of seven types of flavonoids influenced the weight of 124,086 men and women aged 27-65 who were part of the Health Professionals Follow-up Study, the Nurses' Health Study or the Nurses' Health Study II.
Every 4 years between 1986-2011, participants were required to complete a dietary questionnaire, from which the researchers assessed their intake of dietary flavonols, flavones, flavanones, flavan-3-ols, anthocyanins, proanthocyanidins and flavonoid polymers.
Participants' weight, lifestyle habits and diagnosis of any diseases were assessed through a questionnaire completed every 2 years.
Anthocyanins, flavonoid polymers, flavonols linked to least weight gain
The researchers found that participants who increased their consumption of certain flavonoid types - flavonols, flavan-3-ols, anthocyanins and flavonoid polymers - during the study period were less likely to experience weight gain.
Anthocyanins, flavonoid polymers and flavonols were associated with the least weight gain; every additional 10 mg of anthocyanins, 138 mg of flavonoid polymers and 7 mg of flavonols consumed daily were associated with 0.16-0.23 Ibs less weight gained each 4 years.
These findings remained after accounting for potentially confounding factors, including changes to participants' smoking status, physical activity and other dietary aspects.
The main sources of anthocyanins in the study were strawberries and blueberries, while tea and onions were the main sources of flavonols. Intake of flavan-3-ols and their polymers primarily came from tea and apples.
Bertoia and colleagues note that their findings are observational, meaning no definite conclusion can be reached.
Still, the team says the results could help combat the current obesity epidemic by offering guidance on which fruits and vegetables are best for weight maintenance:
"Higher intake of foods rich in flavonols, flavan-3-ols, anthocyanins, and flavonoid polymers may contribute to weight maintenance in adulthood and may help to refine dietary recommendations for the prevention of obesity and its potential consequences."
The researchers add that preventing just small amounts of weight gain can have a significant impact on public health, reducing the risk of diabetes, high blood pressure, cardiovascular disease and some types of cancer.
The authors admit that there are some limitations to their findings. For example, while participants' intake of flavonoids was assessed through a dietary questionnaire, the amount of flavonoids present in foods is likely to have varied depending on food ripeness, food processing, storage and season.
Additionally, they note that the dietary questionnaire may not have identified all food sources of flavonoids, so the results may have underestimated the link between flavonoid intake and weight maintenance.
This research follows another study from Bertoia and colleagues that Medical News Today reported last September, in which the team found intake of low-fiber, higher-glycemic and starchy vegetables - such as peas, corn and potatoes - may lead to weight gain.