The Harmful Effects of being Underweight

This interview is broken into two parts. This is Part 1 and focuses on the effects of being clinically underweight and the second focuses on compulsive exercising.

1.     What are some of the short and long-term side effects of being underweight and the ways people often go about getting their weight so low? Is it life-threatening?

In the short-term one will likely notice problems such as: weakness, fatigue, lightheadedness, inability to concentrate, lower pulse rate, increased emotion fluctuation and amenorrhea (cessation of menstrual cycle). Long-term this can lead to: bone mineral loss, premature osteoporosis where bones can weaken 2-3x faster than would be normal for that age, decrease sexual functioning, short and possible long-term reproductive damage, frequent over-use injuries, altered endocrine (hormone) function, growth of fine body hair on face and arms, extreme sensitivity to cold, difficulty swallowing, swollen glands, blood shoot eyes, damaged teeth and depression.

Yes, if taken to the extreme, this can be life-threatening or least threatening to your quality of life and life expectancy.

References: Nancy Clark’s “Sports Nutrition Guidebook” and Liz Applegate’s “Encyclopedia of Sports and Fitness Nutrition.”

2.     Are these effects any more or less serious than being clinically overweight?

Interestingly enough there is some research to suggest that from mortality perspective it is healthier to be overweight and strong than to be underweight and weak. Just as someone who is legitimately overweight needs to work at getting back down to a healthy weight, one who is underweight needs to work on getting the body back up to a healthy weight.

3.     If someone fears they are at risk of these side effects, what can they do to prevent them and return to a healthy weight?

They need to eat more healthy food and engage in some strength training to build lean muscle and get the body back up to a healthy weight. In some cases, body fat levels are too low (e.g. women under 10-15% body fat) may need to increase their body fat levels up to a healthy level where they resume a regular period.

 4.     Why is strength training important to someone who is recovering from an eating disorder/being clinically underweight?

Strength training is important for several reasons:

  1. It helps to rebuild lean muscle that is lost with extreme dieting. Lean muscle is an important part of being healthy weight.
  2. It helps to increase the metabolism. Extreme dieting and eating disorders lower the metabolism. When one returns to normal healthy eating, he/she has a tendency to gain extra body fat as the metabolism is slower. Strength training raises the metabolism and thus allows one to eat in a way that supplies daily nutritional requirements without the body fat gain.
  3. It helps to rebuild strength which is also low in those who are underweight and very low in those with eating disorders. Strength not only improves our ability to function safely and effectively in our everyday lives, but also improves our confidence and self-esteem.
  4. It builds bones. As mentioned previously, bone density loss is a common problem with eating disorders, extreme dieting and those that are underweight. The stress of resistance training builds not only the muscles but the bones as well. In conjunction with proper nutrition, weight training can assist individual recovery from an eating disorder with rebuilding bone density.

Read part 2


Andrew Heming works at Trinity Western University as an assistant professor and a strength and conditioning coach and performance nutrition consultant for Trinity Western’s Spartan Athletics. Andrew has a Master’s degree in Exercise Science and certifications in strength and conditioning, personal training and performance nutrition.

1 Comment

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  • It is so interesting that being underweight can be as bad, if not worse than, being overweight. It is a fact so rarely put out there!!


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