The Sin of Yo-Yo Dieting

One of the cardinal sins of health and fitness is yo-yo dieting.  It destroys your health.

Yo-yo dieting is a repeated cycle of weight loss followed by weight gain.  At first, this doesn’t appear all that bad.  So, somebody went from 200lbs to 150lbs and back to 200lbs.  Who cares?  Yeah, they’re back where they started, but at least they’re not worse off now!

Unfortunately, they are worse off now.  The body can be a difficult machine to master.  Since your body is entirely concerned with survival and not very concerned about your figure, it doesn’t get along with the yo-yo dieting concept.  Consider the following example:

Alice.  She’s from wonderland.  She’s 165lbs on January 1, but she made a resolution to lose 40lbs.  She goes on a fad diet that tells her to eat 500 calories a day.  Somehow, she sticks with it for three months, and she has lost 40lbs!

Unfortunately, what Alice doesn’t know is that since she severely restricted her calories, half of the weight she lost was muscle mass.  She lost 20lbs of muscle mass and therefore (20lbs * 50 calories per pound) 1,000 calories of basal metabolic rate.  Now when she’s at rest, she burns 1,000 calories less.  She doesn’t realize this, though, and she goes back to eating normally since the whole 500 calories a day thing was too much to handle.

Well, according to Set Point Theory (, Alice’s body will return her to her original weight of 165lbs.  However, her 165lbs now has an extra 20lbs of fat, and her metabolism is now 1,000 calories slower than before.  Here, I’ll show you the numbers assuming she’s an average American woman.

Alice is perfectly average (

January 1 (Before Diet)
Height:  5’4”
Weight:  165lbs
Bodyfat Percentage:  25%
Lean Body Mass:  124lbs
Fat Mass:  41lbs

Summary:  She’s statistically as average as I can possibly make her for an American woman.

April 1 (After Diet)
Height:  5’4”
Weight:  125lbs (40lb loss)
Bodyfat Percentage:  17%
Lean Body Mass:  104lbs (20lb loss)
Fat Mass:  21lbs (20lb loss)

Summary:  Now, she’s lost 40lbs from her overly-restrictive diet with no exercise.  20lbs of that was fat, and 20lbs of that was muscle.  The 20lbs of muscle loss equated to a 1,000 calorie loss in her metabolism, but at least she’s leaner too.

July 1 (After Three Months of Eating Normally Again)
Height:  5’4”
Weight:  165lbs (no change from January 1)
Bodyfat Percentage:  37%
Lean Body Mass:  104lbs (20lb loss from January 1)
Fat Mass:  61lbs (20lb gain from January 1)

Summary:  Set Point Theory jumped in.  Once her body realized that it had survived a starvation period, it took steps to make sure that she doesn’t starve to death in the future.  She did nothing to make her body need to build muscle, so it got back to its prior weight by building body fat.

Now, she is the same weight she was when she started her six-month diet attempt, but she is now 20lbs fatter.  Her metabolism is also 1,000 calories slower.  Any future diet attempts she makes will be much more difficult due to her decreased metabolism.

So, what should she have done?  Physiologically, it’s really quite simple, and it will be answered in respect to her exercise and nutrition.  There will always be emotional and psychological factors, but those are for the experts in those fields.  However, I can and will lay out the most direct path for her to get to her ideal body composition from a purely physiological standpoint.

If you missed part 1, it’s here: