A new study by Harvard researchers has comprehensively shown how much weight gain is associated with eating certain food groups.

People on diets know that wolfing down cheeseburgers and Fries are more fattening than fruits and vegetables. According to the study losing weight is more about eating right than eating less.

Dr. Dariush Mozaffarian, associate professor of medicine and epidemiology at Harvard Medical School and Brigham and Women's Hospitals and lead author of the study wrote that people shouldn't just focus on total calories consumed. "Our results demonstrate that the quality of the diet - the types of food and beverages that one consumes - is strongly linked to weight gain."

Potato chips are the worst offenders in any diet. An extra serving of potato chips eaten in a day will result in an extra 1.69 lbs every four years. Potatoes are also among the other extra-fattening foods along with sugar-sweetened beverages, red meat and processed meat which account for an extra 1 lbs ever four years. Potatoes are extra fattening mostly because people eat them in large quantities and they also cause big spikes in blood sugar and insulin.

According to a Time Magazine report the study was based off data gathered from government- funded trials on diet, lifestyle and health in adults. The study followed the participant over 20 years and found that they gained nearly 17 lbs on the average.

Yogurt was determined to be the best food to eat over time with only 0.82 lbs of weight gained. Other foods to eat are fruits, vegetables, nuts, and whole grains. Alcohol and sleeping more or less than the allotted 8 hours of sleep could also lead to an overweight person.

"It's not that calories don't count; indeed they do. But it's a lot easier to control calories by eating healthfully and avoiding junk foods and sodas than it is to delude yourself into thinking you can count them accurately," says Marion Nestle, professor of nutrition at New York University.

Overall the study only supported what nutritionists and doctors have been saying for years. Eat healthy and exercise regularly to maintain a healthy weight.