A study conducted by researchers from Harvard University has shown that even though eating more fruit and vegetables is widely perceived to prevent long-term weight gain, it should be noted that specific types of fruits and vegetables can actually increase weight, the Sydney Morning Herald reports.

The study involved more than 133,000 adults in the United States. It was found that those who ate an extra handful of blueberries each day lost more than half a kilogram over a four-year period. The other fruits that aided weight loss were apples, pears, strawberries and grapes.

"The benefits of increased consumption were greater for fruits than for vegetables and strongest for berries, apples/pears, tofu/soy, cauliflower, and cruciferous and green leafy vegetables," wrote lead author Monica Bertoia from Harvard's School of Public Health in the latest PLOS Medicine.

"Increased satiety with fewer calories could be partly responsible for the beneficial effects of increasing fruit and vegetable intake."

The study also showed that starchy vegetables such as peas and potatoes increased weight, while non-starchy vegetables helped the participants aided the weight loss.

"We found that many vegetables were inversely associated with weight change, but starchy vegetables such as peas, potatoes, and corn had the opposite association in which increased intake was associated with weight gain," wrote Ms Bertoia.

"Although these vegetables have nutritional value (potassium, vitamin C, vitamin B6, iron, fibre, and protein), they have a higher glycaemic load (lower carbohydrate quality) that could explain their positive association with weight change."

The researchers took into account lifestyle variables such as smoking, exercise and diet.