The prevailing belief that eliminating 3,500 calories from your diet will yield a body weight reduction of 1 lb. is not accurate. The reason is that when individuals lose weight, the body compensates to prevent further weight loss and even promote regain.
The 3.500 calorie rule would predict that an individual who consumes 100 fewer calories per day would lose more than 50 lbs over five years. More accurate weight loss estimates, which take into account compensatory changes of the body, would predict a decrease weight of only 5 lb. But by the third year you could expect to lose 27lbs.
A better rule of thumb for adults is that a maintained deficit of 100 calories per day without any other changes will lead to an eventual weight loss of about 10 lb. over the first year. It will take about one year to achieve 50% and about three years to achieve 95% of the total weight loss.
I you want to accurately predict your weight loss use the simulator found at the following website:
Terry Pfau DO, HMD