Study Informs on Which Fruits and Veggies Best Prevent Weight Gain

Veronica Hackethal, MD

January 29, 2016

Eating more foods high in certain flavonoids may help prevent weight gain over time for adults, according to findings from a study published online January 27 in the BMJ.

"We looked at seven different types of flavonoids, and we found that the classes that were associated with better weight maintenance were flavonol, anthocyanins, and flavonoid polymers," commented first author Monica Bertoia, MPH, PhD, research associate at the Harvard TH Chan School of Public Health, Boston, Massachusetts.

Fruits like apples, pears, and red berries represent the major sources of flavonoids, but they can also be found in some vegetables like red peppers, Dr Bertoia said.

Preventing a Bit of Weight Gain Is Important for Health

The study is the first to look at links between intake of various flavonoid subclasses and weight gain. It included data on over 124,000 women and men in the United States who were followed for up to 24 years.

Past studies have suggested that flavonoids may play a role in weight loss. Most have focused on the flavon-3-ol subclass found in green tea, though, and have had small sample sizes.

The new study drew on data from 124,086 women and men who participated in three prospective studies:  the Nurses' Health Study (NHS), Nurses' Health Study II (NHSII), and the Health Professionals Follow-up Study (HPFS).

Participants were aged 27 to 65 and came from all 50 states of the United States; they self-reported their weight, lifestyle habits, and recent medical diagnoses every 2 years between 1986 and 2011. They also documented their diet every 4 years using validated semiquantitative food frequency questionnaires (FFQs).

Researchers looked at seven flavonoid subclasses: flavanones, anthocyanins, flavan-3-ols, proanthocyanidins, flavonoid polymers, flavonols, and flavones.

They adjusted the results for lifestyle factors linked to weight change, including physical activity, TV watching, and 17 dietary factors such as intake of sugar-sweetened drinks, fried foods, alcohol, caffeine, whole grains, and processed meats.

Results showed that over each 4-year period, women gained an average of 2.9 pounds (NHS) to 4.4 pounds (NHSII), and men gained an average of 2.2 pounds (HPFS).

Though small, even this amount of weight gain "will really add up over the long term," Dr Bertoia pointed out.

"Preventing just small amounts of weight gain or losing small amounts of weight can have an impact on your individual health and risk of cardiovascular disease," diabetes, and cancer, she said, adding, "It can also have a really big impact on population health."

Which Fruits and Vegetables to Target to Prevent Weight Gain

The findings — adjusted for lifestyle factors — suggested that people who ate more foods from specific flavonoid subclasses experienced less weight gain over time.

The following flavonoids had the greatest effect on weight loss: anthocyanins produced −0.23 lbs per additional standard deviation (SD)/day, flavonoid polymers −0.18 lbs per additional SD/day, and flavonols −0.16 lbs per additional SD/day.

Each increase in standard deviation of daily intake was linked to 0.16 to 0.23 fewer pounds (equivalent to 0.07-0.10 kg) gained over 4 years.

After fiber intake was accounted for, the findings remained significant for anthocyanins, proanthocyanidins, and total flavonoid polymers but lost significance for the other subclasses.

One serving per day of many fruits often provides many more flavonoids than one standard deviation, which may put these findings into perspective. For example, eating just a half cup of blueberries per day would increase consumption of anthocyanins by 12 standard deviations.

Foods high in anthocyanins include dark red fruits like blackberries, red grapes, raspberries, cherries, blueberries, and strawberries, with the latter two fruits also high in flavonoid polymers, as are tea, pecans, and apples. Tea is also rich in flavonols, along with onions and some types of beans, Dr Bertoia pointed out.

The observational nature of the study limits conclusions about whether or not the findings are related to overall improvement in diet quality, to the flavonoids themselves, or to something else, according to Dr Bertoia. Other limitations include the use of a self-reported FFQ.

Nevertheless, this paper builds on prior research by this group and "helps to refine the general advice that everyone should eat more fruits and vegetables. It helps give more information about which potential fruits and vegetables may be better choices to make more specific recommendations in future guidelines," Dr Bertoia said

In the United States currently, most people consume less than 1 cup of fruits, and less than 2 cups of vegetables daily. The authors suggest that this should be increased to 2 cups of fruits and 2.5 cups of vegetables.

The authors report no relevant financial relationships.

BMJ. Published online January 27 2016. Article

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