Washington, Oct 22 - Cheeseburgers and fries might look tempting, but eating some broccoli or leafy greens first could help people battle obesity and heart disease, says a new study.

Eating more plant-based foods, which are rich in substances called phytochemicals, seems to prevent oxidative stress in the body, a process associated with obesity and the onset of heart disease, according to the study.

To get enough of these protective chemicals, researchers suggest eating plant-based foods such as leafy greens, vegetables, fruits, nuts and legumes at the start of a meal.

Oxidative stress occurs when the body produces too many damaging free radicals and lacks enough anti-oxidants or phytochemicals to counteract them.

Because of excess fat tissue and certain enzymes that are more active in overweight people, being obese can actually trigger the production of more free radicals, too.

Using a phytochemical index, which compares calories consumed from plant-based foods with the overall number of daily calories, could remind people to get enough phyto-chemicals during meals and snacks, said Heather K. Vincent, University of Florida (UF), who led the study.

"We need to find a way to encourage people to pull back on fat and eat more foods rich in micronutrients and trace minerals from fruits, vegetables, whole grains and soy," said Vincent.

"Fill your plate with colourful, low-calorie, varied-texture foods derived from plants first. By slowly eating phytochemical-rich foods such as salads with olive oil or fresh-cut fruits before the actual meal, you are likely to reduce the overall portion size, fat content and energy intake."

"In this way, you're ensuring that you get the variety of protective, disease-fighting phytochemicals you need and controlling caloric intake," added Vincent.

These findings were published online in the Journal of Human Nutrition and Dietetics. (IANS)