Findings from a new study suggest that eating plenty of fruits and vegetables rich in phytochemicals called flavonoid might help adults minimize weight gain as they age.
Most plants contain different flavonoids in varying concentrations. Scientists believe these naturally-occurring compounds have antioxidant and anti-inflammatory properties that could help explain the health benefits, including protection from diabetes, associated with diets rich in fruits and vegetables.
The researchers, from the Harvard T.H. Chan School of Public Health in Boston, found that a greater intake of fruit high in flavonoids like apples, berries and grapes was associated with less weight gain.
Not all types of flavonoids, however, were linked to reduced weight gain once researchers accounted for how much fibre people ate.
The goal of the research was to determine which fruits and vegetables may be best for weight maintenance in order to refine dietary guidelines that currently recommend eating more fruits and vegetables but don't clearly specify which fruits and vegetables are better than others for the prevention of obesity.
To examine the connection between flavonoids and weight, the research team analyzed data about 124,000 U.S. health professionals collected between 1986 and 2011.
Participants reported their weight every two years and completed dietary questionnaires every four years.
Based on what people said they ate, researchers used U.S. Department of Agriculture data on flavonoid content in specific foods to determine how much of these compounds participants consumed.
Reduced weight gain small, but can make a different over time
Across all the studies, half of the participants consumed at least 224 milligrams to 247 milligrams of flavonoids a day (equivalent to about 5 servings of flavonoid-rich foods per day).
Over each four-year period, people gained an average of 2.2 to 4.4 pounds.
But people with higher than average flavonoid consumption tended to gain slightly less weight.
The difference amounted to about one-tenth to three-fifths of a pound over four years for each standard deviation above the average amount of flavonoid consumption.
For example, consuming 7 milligrams more flavonols - a subtype of flavonoids found in tea and onions - than average each day was associated with gaining roughly one-sixth of a pound less weight over four years.
The researchers adjusted for factors that can influence weight including age, gender, exercise, smoking, alcohol, caffeine, sleep and sedentary television time. They also accounted for other things people consumed, such as juice, fried foods, whole versus refined grains, full-fat versus low-fat dairy, sodas, processed versus non-processed meats, trans fats and seafood.
Berries, tea, onions and apples protective
After adjusting for fibre consumption, which may influence weight gain by decreasing how much fat people absorb, only three types of flavonoids were associated with reduced weight gain in the study: 1) anthocyanins, which came mainly from blueberries and strawberries in participants’ daily diets; 2) flavonols and 3) flavonoid polymers, which came mostly from tea and apples.
Limitations of the study include its reliance on survey participants to accurately report what they ate and how much they weighed.
Still, the findings suggest that choosing high flavonoid fruits and vegetables such as apples, pears, berries and peppers may help with weight control.
It's also possible, however, that people who eat more fruits and vegetables may have an easier time with weight management because they consume a healthier diet and eat fewer calories. It could also be that these people are more health conscious than others.
Source: The BMJ, online January 28, 2016.
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