The starvation myth

The idea that 'not eating enough' causes the body to stop losing weight because it goes into 'starvation mode' is a popular myth among dieters.
Starvation myth

Metabolism slows during kilojoule restriction
Restricting kilojoules during weight loss lowers metabolism1 because the body becomes more efficient, requiring fewer kilojoules to perform the necessary daily functions for survival. Consequently, this can slow (but not stop) the anticipated rate of weight loss.

For example, if an individual needs 8,400 kilojoules per day to maintain weight, reducing intake to 6,300 kilojoules, assuming exercise stays the same, should provide a 500g per week weight loss (Note: 500g of weight is equivalent to about 14,700 kilojoules). Furthermore, reducing to 4,200 kilojoules should result in a weight loss of 1kg per week and going down to 2,100 kilojoules a day should result in a weight loss of 1.5kg per week. However, if an individual actually reduces their intake to 2,100 kilojoules, the weight loss would not likely be a steady 1.5kg per week because of the reduced metabolic rate. It would likely be around 1kg. This 'lower than expected' rate of weight loss is a lot different to 'no' weight loss as the 'starvation mode' notion proposes.

It is unclear as to whether the relationship between reduced kilojoule intake and a lower metabolism follows a straight path or becomes more pronounced the greater the kilojoule reduction. Some studies have found no significant reduction in metabolism until the kilojoule restriction is quite large (e.g. 3,360 kilojoules or less per day).2 Others suggest a linear relationship with small reductions in metabolism accompanying small reductions in kilojoule restriction, with the gap increasing as the kilojoule deficit is enlarged.

While there is no biologic evidence to support the 'starvation mode' myth, there may be behavioural reasons why weight loss stops when kilojoules are severely reduced. Over-restriction of kilojoule intake, known as high dietary restraint is linked to periods of overeating, hindering successful weight loss.3 (For more information on dietary restraint, read the Science Centre article)

Metabolism after weight loss
The good news is that after the weight loss goal is achieved and weight has stabilised, it does not appear that the dip in metabolism is permanent. Several rigorous studies done at the University of Alabama in Birmingham showed that metabolism goes back to expected levels with sustained weight loss,4 discounting the theory that a lowered metabolism helps to explain the common phenomenon of weight regain following weight loss.

Weight Watchers approach
The ProPoints Plan® is designed to provide a kilojoule intake that supports a healthy rate of weight loss, produces a minimal reduction in metabolism and avoids inducing too-high levels of dietary restraint.

This content is reviewed regularly. Last updated December 17, 2011.

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FOOTNOTES
1 Saltzman E, Roberts SB. The role of energy expenditure in energy regulation: Findings from a decade of research. Nutr Rev. 1995. 53:209-220.
2 Burgess NS. Effect of a very-low calorie diet on body composition and resting metabolic rate in obese men and women. J Am Diet Assoc. 1991 Apr;91(4):430-4.
3 Rogers PJ. Eating habits and appetite control: a psychobiological perspective. Proc Nutr Soc. 1999 Feb;58(1):59-67.
4 Weinsier RL, Nagy TR, Hunter GR, Darnell BE, Hensrud DD, Weiss HL. Do adaptive changes in metabolic rate favor weight regain in weight-reduced individuals? An examination of the set-point theory. Am J Clin Nutr 2000 Nov;72(5):1088-94.