I’ve heard this refrain for decades ” eat less than you burn and you’re sure to lose weight”.
Here are a few points that are sadly left out of this piece of widely popular “advice”.
The truth is; depending on Gender, Age, Fitness level and Weight … “eating less than you burn” can actually slow down your metabolism and make you store fat!
Here’s how and why! Let’s start with a glossary of terms:
Basal Metabolic Rate. The amount of calories that your body requires each day just to maintain normal functions of life … not including any physical activity or exercise. This is measured in kcal / day.
Body Mass Index. This number is the ratio of your height to your weight. The BMI chart will list you as Underweight, Healthy, Overweight, Obese or Very Obese.
Body Mass. Your Body Weight.
Body Fat Percentage. The percentage of your Body Mass that is fat. We all need a certain amount of body fat to keep us healthy and for all of our organs and our endocrine system to function properly. Different levels of Body Fat are considered healthy based on Gender and Age.
Metabolically Active Tissue. Tissue on your body that actually burns calories, raises your metabolism – even while resting. Muscle, skin, bone and organs are examples of Metabolically active tissues.
Lean Body Mass. This is the amount of Metabolically active tissue on your body. Muscle and water are both large components of LBM. In fact, Muscle is comprised mostly of water!
Too often I talk to people who are working out consistently and are not obese but who have decided that they’ll just try to cut back on eating to try to lose weight.
Let’s take “Jane” – She is 5″ 5′ and 155 pounds, BMR is about 1,500 kcal per day, she is 30% body fat and her BMI is 25. Jane decides to “diet” and reduces her calories to about 1,000 calories a day. And start an exercise program. That represents about a 34% difference between caloric intake and caloric (energy) expenditure. Factor in the extra 300-500 calories she’s burning from exercise and daily activity now the gap is even bigger!
Over a period of time, what Jane’s body does in order to close the gap between intake and expenditure is the exact opposite of what she wants … her body lowers BMR to save energy and to compensate for the reduced intake and burns less calories than before and now resorts to saving those calories as fat (stored energy). Jane may lose weight initially but then her body slows down it’s fat burning. She does lose weight, however most of what she loses is water and muscle. Because remember her basal metabolic rate is now lower because she has lost lean body mass!
Now – Jane switches to an eating lifestyle of multiple small meals throughout the day consisting of whole, non-processed foods. She increases her calories to about 1,500 kcal/day. She also stays hydrated by drinking 1/2 oz. of water per lb of body weight daily.
Her body is now satisfied that it has enough energy to do all that it needs to do daily (she’consuming just a few 100 calories less than she’s burning) and that food is not scarce and her muscles and organs are properly hydrated now her body can function properly and safely start to get rid of the extra fat tissue that it has stored.
Jane can eat and exercise and burn fat and she’s healthier and happier!