Food intake and weight gain. if we increase our food intake, we generally gain weight. nutrition scientists can calculate the amount of weight gain that would be associated with a given increase in calories. in one study, 16 nonobese adults, aged 25 to 36 years, were fed 1000 calories per day in excess of the calories needed to maintain a stable body weight. the subjects maintained this diet for 8 weeks, so they consumed a total of 56,000 extra calories. according to theory, 3500 extra calories will translate into a weight gain of 1 pound. therefore, we expect each of these subjects to gain 56,000/3500