Why you need to know your BMR before setting any fitness goals
Many people try to follow a calorie-controlled diet. But to lose, gain or maintain weight you must have an idea of your daily calorie requirement. To lose weight, the calories taken in from food and liquid must be less than the calories expended. To gain weight, the calories taken in from food and drink must be more than the calories expended. Finally, to maintain weight, there has to be a balance between the calories consumed and the calories expended. Knowing your daily energy costs is an important part of your weight management program.
Energy costs can be divided into three main groups, the basal metabolic rate, (BMR) which is solely the cost of running your life support system, heart, lungs, digestion etc. Daily expenditure, which is what you do when awake up and about and finally the energy costs of exercise.
BMR is related to age and gender, with women holding a proportionally higher level of fat and less muscle tissues than men. Muscle tissue is metabolically more active than fat tissue therefore requires more energy to maintain.
If anyone has ever given you a calorie controlled nutrition plan without knowing your BMR then you may be misinformed. I have seen a BMR difference of 500 calories in 2 separate females of the similar weight and age. 500 calories per day over a year is 182,500 calories or approximately 23kg of body fat.
Under eating- This is where we see a lot of people going wrong, whilst you need to be in calorie deficit to reduce body fat if you drop your calorie intake below you BMR (calorie amount you need just to survive) your body needs to adapt for survival. It will do this by reducing your lean muscle to lower your BMR so you need less calories. You then eventually go to your normal eating habits but your BMR is now lower so you need less calories and you put the weight back on and maybe some more.
Example- Female A wants to lose 10kg body fat she starts a 1200 calorie nutrition plan and starts running on the treadmill after a few weeks she has lost 3 or 4 kg which she is really happy about. All of a sudden things slow down, her energy levels are dropping and food cravings start kicking in so the 1200 calorie plan goes out the window, the treadmill gets boring and the weight creeps back on.
Lets look at what is actually happening here:
Female A needs 1400 cal per day just to survive at her current body composition, consuming under this amount will cause her body to adapt to be more efficient so it can survive on the 1200 cal it is currently receiving. To do this it will try to reduce the amount of lean muscle it has (especially if not actively using it) to reduce her BMR from 1400 back to 1200. A few weeks in after the diet is long gone her calorie intake is back to 1600cal per day but her new BMR, due to less lean muscle, is now only 1200cal. As you can see from this example the diet not only didn’t work it’s left her in a worse position than when she started.
What should had happened: Female A knows her BMR is 1400cal, a nutrition plan (not a diet) is created based on eating 1400cal per day, she starts some strength training 2 to 3 times per week to increase her lean muscle.
The calorie equation: Calories in 1400 minus 2400 Calories out (the 2400 is a total of her BMR (1400)+daily activities + Training) = 1000 cal deficit.
4 weeks in Female A has lost 3kg all from fat her BMR has now gone from 1400 to 1450 so she can add another 50cal to her food intake. She is now fitter, stronger, leaner and her body requires more calories without doing any more effort which makes maintaining the fat loss easier.
Before you start any health or fitness goal find out what your BMR is and base your nutrition around this.
Whilst Calories in V’s Calories out is the main decider of what your weight does over time the quality and macro makeup of those calories plays a big part to your overall health.