As I counsel patients about their health and weight loss goals, a common refrain from patients is that their “metabolism” is slow so they cannot lose weight. I am empathetic because I have struggled with my weight. No matter what I did, I could not lose weight and be fit like I observed others do. We all know people who seem to be able to eat whatever they want, and they remain thin. I acknowledge that some people seem to have an easier time being thin than others. Many of us seem to gain weight just by thinking about food! Here are the facts about metabolism and metabolic rate.
Metabolic rate is a measure of how much food, or fat, is converted to energy in a day. Resting metabolic rate (RMR) is the measurement of how much food, or energy, is required to maintain basic body functions such as heartbeat, breathing, and maintenance of body heat while you are in a state of rest. That energy is expressed in calories per day. So, an RMR test shows how many calories you burn at rest, doing nothing more than sitting in a chair.
Total daily energy expenditure’s primary components are:
1. resting metabolic rate 60-75%
2. diet-induced thermogenesis 10%
3. activity thermogenesis- exercise energy expenditure and non-exercise activity 15-30%
Resting metabolic rate is your metabolism. It can be affected by hormone levels, thyroid function, and other processes in your body. Studies show that it is also affected by your gender, race, age, and other variables. But, as I review the various studies, if I consider all of the various factors that influence metabolism and I run the worst case scenarios, I find that the variability in resting metabolic rate is only a few hundred calories. If the predicted resting metabolic rate of a person is 1800 calories per day, the largest, worst case variability for that person would predict a resting metabolic rate of 1100 calories per day. (60%) One study found that 96% of people are within 10-15% so 60% is beyond a worst case scenario.
So, let’s think about that 700 calorie deficit. 700 calories is less than:
- a double at Wendy’s
- just over 2- 20oz bottles of coke
- 2 orders of fries at McDonalds
- 2 chicken breasts
700 calories is also equal to 60 minutes of moderate exercise.
I know that there are many variables in this metabolism question, but I want to encourage people to consider that their “metabolism” is not the primary reason that they have a few extra pounds. The real reason that we are all overweight is that we do not eat the proper portion sizes and we consume too many carbohydrates (which lead to chronic elevated insulin levels)
Consider your nutrition habits. Be honest with yourself. No judgement here and I would encourage you to not judge yourself. I start all patients with an HONEST account of what they are eating. You must know where you are and what you are doing if you want to change your life. To change your life, you must know your life. So many of us are completely unaware of what our nutrition is. Keep a 5 day food journal. I know that this sounds silly. Do not roll your eyes! Simple write down everything that you eat or drink for 5 days. Start with doing it for only one day. You can also use the MyFitnessPal app on your phone. It is a free app provided by Under Armour.
You can have the health and body that you want. You just have to begin!
References:
Korr Medical Technologies
The American Journal of Clinical Nutrition, Volume 82, Issue 5, November 2005
Med Sci Sports Exercise 1989 Oct;21(5):515-25.
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