Q: How is my current calorie intake at the bottom of the calculator determined?
A: This estimate is determined using a formula that depends on your age, height, gender, and current weight. The formula assumes you are weight stable.  This means that you're not currently losing or gaining weight.

Q: The current calorie intake at the bottom of the calculator seems a lot higher than what I think it should be.  Why?
A: The current intake formula was fit to data from a large group of individuals that varied in age, gender, height, and weight. However, despite the quality of the database, the formula still only explains about 60% of the variation in intake between individuals. What this means is that remaining 40% of the variation in calorie intake between individuals is due to factors other than age, height, gender, and weight. For example, variation may be due to how much routine physical activity you conduct on a daily basis or fluctuations in your weight that deviate from weight stability. With a physical examination and more direct clinical measurements, we could provide improved estimates than the one provided here with only knowledge of your age, height, weight, and gender.

Q: Does the calculator include the effect of my metabolism slowing during weight loss?
A: Yes, it does.  However, keep in mind that that the magnitude of calories conserved due to the slowing of your metabolism, referred to as “metabolic adaptation”[1], is not very large and ranges between  50 and 100 Calories per day.

Q: If the lack of weight loss I see is not due to the slowing of my metabolism, why am I not losing weight?
A: This is a challenging question whose answer may be dependent on an individual’s characteristics  that are out of the scope of a model's capacity to predict.  The best recommendation is to contact your healthcare provider and discuss your weight patterns with them.

Q: Did the study cited in the New York Times[2] find that even if I increase the calories I burn through exercise, I will end up not losing weight?  That seems so counterintuitive.
A:  The study was actually designed to find out why individuals do not lose weight, especially because they are burning more calories. The study examined all possibilities using a rigorous mathematical approach.  The study established that vigorous exercise did result in increased food consumption.  The study also determined that metabolism slowed during vigorous exercise if intake remained unchanged.  Additionally, the study also established that lean (muscle) mass decreased less during aerobic exercise in comparison to diet restriction.  We found that a larger fraction of weight gained (if one gained weight) during exercise is gained as lean mass.  That is, if you lose weight through exercise, you lose mostly fat mass, and if you gain weight during exercise, you gain mostly lean mass.  This is good news for all of us who want to lose fat.

1. Martin, C.K., et al., Effect of calorie restriction on resting metabolic rate and spontaneous physical activity. Obesity (Silver Spring), 2007. 15(12): p. 2964-73.

2. Thomas, D.M., et al., Why do individuals not lose more weight from an exercise intervention at a defined dose? An energy balance analysis. Obes Rev, 2012.