Harvie, M. N., Pegington, M., Mattson, M. P., Frystyk, J., Dillon, B., Evans, G., … Howell, A. (2011, May). The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: A randomized trial in young overweight women. International Journal of Obesity (London), 35(5), 714–727. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017674/
As we mentioned above, eating in a calorie deficit is key. Jim recommends eating 500 calories less than your total daily energy expenditure, or TDEE. This is the number of calories you burn in a day, which is based on factors like age, height, sex, and activity level. To calculate what this number is and what your calorie target should be to lose weight, use this formula. Just make sure you don't go below 1,200 calories a day for women; in a previous interview, Jim said eating any fewer calories than that can slow down your metabolism and result in negative side effects like low energy, loss of hair, hunger pangs, and a negative impact on your menstrual cycle.