Most people overestimate the effort required to maintain their weight and don't realize simple lifestyle changes can help them prevent weight gain. An American Council for Fitness and Nutrition national telephone survey of 1,044 adults aged 18 and older found 40 percent of the respondents incorrectly believe that in order to prevent weight gain, people need to reduce their daily caloric intake by at least 500 calories. But a recent study says that reducing caloric intake by just 100 calories a day may be all that's necessary to avoid weight gain. The survey also found that many people overestimate what they need to do in terms of eating better and being more active to reach that 100-calories-a-day reduction. The council has a 50/50 program that offers tips on how people can eat 50 calories fewer and burn 50 calories more each day. Women were more likely than men to underestimate the ease of cutting 50 calories per day through dietary changes and burning 50 calories a day by increasing their physical activity. More than a third of the respondents said they believed they would need to walk briskly for 30 minutes to burn off an additional 50 calories per day. Only 13 percent of the respondents knew that the average person only needs to walk 10 minutes to burn off those 50 calories. Just 16 percent of the respondents knew that eating two less tablespoons of ice cream per day eliminates 50 calories. The council is a coalition of food and beverage companies, trade associations and not-for-profit organizations.