When it comes to flexible dieting & IIFYM, BMR is where it all starts

BMR = Basal Metabolic Rate (similar to RMR = Resting Metabolic Rate, but for flexible dieting purposes, it is slightly different)
Your BMR is represents the number of calories your body burns at rest. The IIFYM BMR calculator will calculate the precise amount of calories your individual body requires to keep you alive. The BRM Calculator is not a TDEE Calculator so you should not base any dietary decision on the number our BMR calculator spits out. Flexible Dieting is more than just not eating. It is a very precise method of fat loss that works!

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Many people that are flexible dieting make the mistake using the IIFYM BMR calculator to tell them how many calories to eat. Doing this can lead to too drastic a calorie deficit leading to muscle loss, and stalled fat loss. It can also cause a drastic rebound effect, something many YO YO dieters have experienced. Remember, BRM & TDEE are not the same thing!

The IIFYM BMR Calculator should only be used to figure out the exact amount of calories your body needs to stay alive. This does not include getting out of bed, exercising, or even opening your eyes.
If you are trying to figure out how many calories you need to eat in order to lose weight and burn fa while flexible dieting, please do not use the BMR calculator. Instead use the IIFYM TDEE Calculator which will calculate your BMR along with all the other calories your burn during the day. The IIFYM calculator is perfect for people that are flexible dieting that do not want to burn muscle and want to focus on fat loss.