Expert: Ryan Hale - 9/12/2011

Question
I have a friend that limits caloric intake between 1800 to 2200 per day.  This past Saturday, my friend went on a bike ride of an hour and a half average 22mph. The total caloric intake was 2000 calories. He is male 5'10.5.  On Sunday, he only had 700 by 2:00 and we were going to go for a ride that typically burns 300 calories. I was afraid to go on the ride with him because I was worried about his caloric intake.  Can you please explain if it is healthy or unhealthy and what are the short and long term effects of this behavior please?
Thanks,
Leslie

Answer
Calorie restriction is not health unless someone needs to lose weight for health reasons.  In that case, calories can be restricted at a slow rate (by a few hundred calories per day depending on the weight loss need).  For most others, calorie intake needs to meet the energy demand on the body.  When it comes to exercise, we are not very good at estimating the amount.  research shows that people typically tend to replace around 200 calories more than they burn during exercise.  Generally though our calories need to meet demand for energy.  If the goal is weight loss, the intake needs to be slightly less than how much is needed.

For someone of normal weight, that is, they don't need to lose weight, it is not healthy for the body to not meet its energy needs.  First, out blood sugar is affected.  Having drops in blood sugar can lead to agitation, confusion, irritability, dizziness, visual problems and passing out.  Longer term, this can lead to the body storing fat and low energy.  The digestive system can be affected and the amount of time it takes for food to pass through the digestive system can become such that the person feels very uncomfortable and bloated when they do eat.  Body functions are affected without enough calories, including the heart, skin, brain, muscles, teeth, sexual function, and bones.  For serious cyclists, this is of particular concern since often they have low bone mineral density anyway due to the nature of the sport.

When one dies of a serious eating disorder, it is usually due to heart failure.