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3 Variables to Lose Weight

Darleen Barnard is board certified health coach and personal trainer who specializes in weight loss by using the power of the mind.


The 3 Variables

Why does it seem like it is easier for one person to lose weight than another? Why can two people eat the exact same thing and one person loses weight while the other person gains weight? Why can we eat more calories one week and lose weight and then eat fewer calories the next week and gain weight? Why can we exercise like crazy one week and gain weight and then not exercise the next week and lose weight?

The answers to all of these questions come down to 3 basic variables, or our energy requirements: Basal Metabolic Rate (our metabolism), Thermic Effect of Food (what we eat), and Thermic Effect of Physical Activity (how much we move).

1. Basal Metabolic Rate

Basal Metabolic Rate (BMR) is the rate at which our bodies expend energy to maintain basic survival. This is what we usually mean when we are referring to our metabolism. Basically, BMR is the number of calories we need just to sit idle and maintain basic body functions. BMR is calculated in the morning when a person is awake but is lying still after a restful sleep and overnight fast. BMR represents as much as 75% of our total energy requirements.

BMR will vary by individual based on several different factors. In general:

  • BMR will be higher if body weight is higher - the more we weigh, the more calories we require for basic survival. This is the reason we need to reduce our calories as we lose weight and we sometimes hit a plateau.
  • BMR will be higher if body mass is leaner - muscle requires more calories than fat. Build more muscle and burn more calories.
  • BMR will be higher for men than women due to the differences in muscle mass (men tend to be more muscular than women)
  • BMR will be higher in younger adults than the elderly primarily due to muscle mass (younger adults tend to be more muscular than the elderly)
  • BMR may also be impacted by hormone imbalances, fever, stress, starvation, or other metabolic abnormalities

Since BMR represents ¾ of our energy requirements, this is the reason why two people who eat the exact same thing will see different results. If a man who weighs 200 pounds consumes 2,000 calories, he may lose weight, while a woman who weighs 140 pounds consumes 2,000 calories, she may gain weight.

Scale to Calculate BMR

2. Thermic Effect of Food

Thermic Effect of Food (TEF) refers to energy required to digest and metabolize the food we eat. TEF represents approximately 10% of our energy requirements. As a general rule of thumb, if we eat 1,500 calories per day, we will burn approximately 150 calories (10%) just to digest at metabolize the food consumed.

Not all calories are created equal though. Some foods are harder for our bodies to break down; therefore, our bodies burn more calories to digest the food. For example, our bodies have to work harder to break down proteins over carbohydrates or fats. For example, if we consume 100 calories of protein, we may burn 25 calories (25%) just to break down the protein, resulting in a net calorie consumption of 75 calories. On the other hand, if we consume 100 calories of carbohydrates, we may only burn 5 calories (5%), resulting in a net calorie consumption of 95 calories. Although there are a lot of factors, this could be one reason why we eat more one week and lose weight and then eat less the next and gain weight.

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3. Thermic Effect of Physical Activity

Thermic Effect of Physical Activity (TEPA) refers to the energy required for physical activity. A sedentary person will have less energy requirements than an athlete; therefore, TEPA represents 15-30% of our total energy requirements. TEPA varies based on activity. As an example, walking at a rate of 4.5 mph is estimated to burn .048 calories per pound per minute; whereas, running at 6 mph is estimated to burn .074 calories per pound per minute.

It is also important to remember, that our body weight will determine how many calories we burn. In general, a heavier person will burn more calories than a lighter person doing the exact same activity.


Calorie Deficit To Lose Weight

In general, 3,500 calories = 1 pound of fat stored. Therefore, we need to have a deficit of 3,500 calories to lose 1 pound. Most experts agree that the safest way to lose weight is to gradually lose weight at a rate of 1-2 pounds per week.

To lose 1 pound per week, we need to have a calorie deficit of 500 calories per day (3500/7 days). This is a NET deficit – if you burn a lot of calories exercising one day, you can eat more that day and still have a deficit of 500 calories for the day. You can create a calorie deficit by eating less or exercising more, although food consumption is much more effective at creating a deficit.

You Cannot Out-Exercise a Bad Diet!!

Important: Women should never consume less than 1,200 calories per day and men should never consume less than 1,500 calories per day without physician supervision

How to Figure Out Your Energy Requirements

Based on your gender, age, height, weight, and activity level, you can determine your Total Daily Energy Expenditure (TDEE). TDEE is an estimate of how many calories you need to MAINTAIN your weight. There are a lot of calorie calculators out there, but a really good one that I would recommend can be found here. Not only does it estimate your caloric requirements, but it also lets you play with your goal weight and lifestyle changes so you can easily see the effect of the changes you make.

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2018 Darleen Barnard


Louise Powles from Norfolk, England on March 24, 2018:

Thanks for the advice. It's never easy losing weight, but I am determined to do so!

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