raw-food-health

Do Metabolic Rates Vary?


Persimmon Metabolic RateIn raw food circles, we're often told that metabolic rates don't vary much from person to person, or that the differences are insignificant.

But you probably know an overweight person who doesn't seem to eat much, or someone who stuffs themselves silly without putting on a pound.

The discussion is complicated by the fact that varying levels of bowel health can lead to drastically different calorie absorption rates. Those with impaired bowel health may only absorb a fraction of the calories they swallow, and can get away with eating a lot more then they need.

But the rate at which we burn the calories we do absorb can vary pretty dramatically.


How Much Do Metabolisms Vary?

 

When looking at the extreme ends of the spectrum (those with the very fastest metabolisms vs those with the slowest), there can be huge differences between people. However, these big differences are rare.

If we restrict the discussion to two standard deviations of the population (96% of us), metabolic speed is within 10 to 16% of the group average (1).

Assuming an average of 2,000 calories a day, that would mean that 96% of us would fall between 1680-2320 calories a day. Roughly half the population has metabolic rates which are within 200 calories of each other, or the food equivalent of two bananas a day (1).

If we tracked down someone at or below the 5th percentile and someone at or above the 95th percentile, we could see a difference of 600 or more calories a day, or the equivalent of a small meal. However, the odds of two random people having such a difference between them is about 0.50% (1).


Are You Stuck With The Metabolism You Have?


Although there can be considerable differences between metabolic efficiency, making the right decisions, and avoiding mistakes can help speed yours up a bit.

 

Metabolic Speed And Exercise


Exercising burns fuel, which creates a caloric deficit. This deficit is at the heart of most exercise-induced weight loss.

However, exercise also has the interesting side effect of temporarily increasing metabolic rate by 1 to 2% (1).


Muscle And Metabolism


Spring Muscle Metabolic RateOne of the most long lasting ways to increase metabolic rate and lose fat is actually to gain muscle mass.

When you add muscle, the percentage of your body made up of fat goes down. So even if you don't actually burn off any fat, you look better.

But the muscle mass you add through strength training is more metabolically active than fat, and requires more calories to maintain itself. When your lean mass increases, your metabolic rate does too (2).

In one study done on elderly adults, a twelve week strength training regime resulted in an impressive 15% increase in resting metabolic rate (3, 4). That's probably enough of an increase to make up for a slower-than-average metabolism in the majority of the population.


Disease And Metabolism


A number of diseases and disorders decrease your metabolic rate.

The most common are those affecting the thyroid, such as hypothyroidism, iodine deficiency (goiter), Hashimoto's disease, and Grave's disease.

When something like hypothyroidism is fixed, there tends to be a significant weight loss. One study showed that treatment of hyperthyroidism resulted in an average of 9.4 pounds of weight loss (8).

The American Thyroid Association believes that those suffering from hypothyroidism may be carrying around an extra 5 to 10 pounds of body weight (9).


Starvation Dieting And Metabolism


One of the things I try to emphasize with my coaching clients is that they should never maintain large caloric deficits (a deficit of 500 calories or less is ideal) when trying to lose weight. Doing so almost inevitably backfires and leads to yo-yoing.

Large calorie deficits and rapid weight loss leads to loss of muscle (or at least a reduction in its functionality and size due to glycogen depletion and water expulsion) (5,6) and a repression of metabolic rate (7).

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I've had several coaching clients who rapidly lost weight on raw food starvation diets. They were happy with their new weight, but had so repressed their metabolism that they were hungry all the time, and gained weight when they satisfied their hunger. They also suffered from a low libido, low energy levels, and a lack of desire to exercise and play.

Don't make the mistake of arriving at your ideal weight with your metabolic rate in the toilet and no energy to thrive.

If you want to lose weight, remember that a small, steady caloric deficit combined with intense physical exercise is your best course. Muscle is your friend, and strength training is what you need to get it.

Make sure you eat enough to fuel an active life.


Can You Rev Up Your Metabolism By Eating More?


The 1967 Vermont Prison Study fed inmates ridiculous amounts of calories with the goal of increasing body weight by 25%. But no matter how many calories they shoveled down their throats, some of the inmates could not reach their target. One inmate eating an incredible 10,000 calories a day could not increase his body weight beyond 18% of his norm.

Metabolic RatesThe study lead some to question the traditional calories in vs calories out model of weight control, and to suggest that it may be possible to increase metabolic rate through eating more food.

However, all the inmates got fatter, and did not return to their prior weight until they resumed their previous calorie intake.

Although there's some anecdotal evidence of people losing weight by eating more calories, there is currently no solid science to support the idea. It's also not clear that a theoretical increased metabolic rate brought about by overfeeding would be enough to compensate for the increased body fat and ongoing higher caloric intake.


Does Eating More Or Less Often Change Your Metabolism?

 

We're often told to eat many small meals to “keep out metabolism stoked”.

However, a meta-analysis review of the published literature on meal frequency shows there's no evidence changing how often you eat will have any effect on metabolism (10).

This goes for both intermittent fasting (eating less often) and eating many small meals. Although both regimes can lead to weight loss, it's only because adherents are eating fewer total calories.

The only relevant factor seems to be the total amount of energy consumed, not when those calories are consumed.

For a more in depth review of this topic, read my article here.


The Implications Of Metabolic Difference

 

Even those with fairly slow metabolic rates are not doomed to be overweight. My own amateur calculations indicate that my metabolic rate is between 300 and 400 calories slower than the prediction of the popular Harris Benedict Equation, which is used in many online caloric calculators.

Yet I've had no problems shedding pounds without feeling deprived or hungry.

I talk about how I was able to lose more than 60 pounds in my book, Raw Food Weight Loss And Vitality, and suggest ways that others can too.

Through a healthy raw food diet and good exercise routine, you can reach a healthy weight and feel amazing, regardless of where your metabolic rate is.


Following Up


Learn about the healthy raw food diet that can get you on a path toward sustained weight loss, regardless of metabolic rates.

Find out what foods are healthy, and which ones you should avoid.

Learn more about raw food weight loss.


Sources:


1) Donahoo WT, Levine JA, Melanson EL. Variability in energy expenditure and its components. Curr Opin Clin Nutr Metab Care. (2004)

2) Astrup A, et al. Prediction of 24-h energy expenditure and its components from physical characteristics and body composition in normal-weight humans. Am J Clin Nutr. (1990)

3) Campbell, Wayne W., et al. “Increased energy requirements and changes in body composition with resistance training in older adults.” The American journal of clinical nutrition 60.2 (1994): 167-175.

4) Byrne, H. K., and J. H. Wilmore. “The effects of a 20-week exercise training program on resting metabolic rate in previously sedentary, moderately obese women.” International journal of sport nutrition and exercise metabolism 11.1 (2001): 15.

5) Senechal, Martin. Et al. Effects of rapid or slow weight loss on body composition and metabolic risk factors in obese postmenopausal women. A pilot study. Appetite V 58. Issue 3, June 2012, Pages 831–834

6) Forbes, Gilbert. Exercise and Lean Weight: The Influence of Body Weight. Nutrition Reviews. Volume 50, Issue 6, pages 157–161, June 1992

7) Leibel, RL. Et al. Changes in energy expenditure resulting from altered body weight. N Engl J Med 1995 Aug 10;333(6):399.

8) Crocker MK, Kaplowitz P. Treatment of paediatric hyperthyroidism but not hypothyroidism has a significant effect on weight. Clin Endocrinol (Oxf). (2010)

9) Thyroid.org: Thyroid and Weight: http://www.thyroid.org/weight-loss-and-thyroid/

10) Bellisle F, McDevitt R, Prentice AM. Meal frequency and energy balance. Br J Nutr. (1997)



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