As someone who’s recovered from an eating disorder this topic has plagued me for a long time. You hear horror stories of yo-yo dieters that are unable to lose weight because years of starvation lead to a metabolism that basically doesn’t work anymore. I’ve often said things myself such as, “I probably screwed up my metabolism for life!” or “These years of dieting have really done me in.” I decided to get rid of these thoughts and instead search through my great old buddy, PubMed. PubMed is a giant database of scientifically published articles about anything and everything science related. So I took an entire afternoon researching how metabolism fairs long-term and short term in recovering anorexics.
My first study looked at the differences between resting energy expenditure (REE, you may be used to calling this your BMR) and respiratory quotient (RQ) between recovered anorexics who’ve been recovered for 2 years and women who were never anorexic. The conclusion? No difference. Recovered anorexics had a higher rate of fat oxidation (the body’s ability to break down big fat molecules and use them for energy), but even then the differences in body composition were basically null. Anorexics two years out of recovery had about the same BMR as those who were never anorexic.
I didn’t stop there.
This study on adolescents followed anorexics during starvation and during refeeding. This study is slightly older (1997) but has been a source for a lot of research since then. They compared the theoretical BMR/REE of starving anorexics using the Harris-Benedict equation and found that anorexics had an even LOWER BMR/REE than they thought. When you’re starving, your BMR/REE is lower than hypothesized. As the study went on they re-did this measurements. They found that their BMR increased significantly within the first two weeks of refeeding (anywhere between 72-85% of what was predicted based on the previous equation mentioned). In conclusion, anorexics who are fasting/starving have a lower BMR to adapt to decreased food intake. As they were refed, their BMR increased within predicted parameters. It’s important to note, too, that it had no affect on energy intake or thyroid function.
What about in those of us who are within the first weeks of recovery and are slowly gaining weight? How much of that is fat?
This study didn’t directly test that, but gave some important evidence to suggest an outcome. The main purpose of this study was to find a good way to track weight gain. Should skin fold tests or underwater weighing be used? Any of us who’ve used an online calculator or BMR know that those things can tell us 8 different numbers on any given day. This study was similar. They found that 55.5% of weight gained back was fat. Ouch. But don’t fret – look at the previous studies. It levels out. Reading into the conclusion they hypothesized that this was mostly due to the fact that anorexics often have EXTREMELY low body fat percentages. To gain weight and only half of it be fat isn’t really as bad as it seems. Plus, this study found that anorexics had a high use of carbohydrates during overnight fasting. Basically, anorexics metabolized carbohydrates at a higher rate than normal. It makes sense that refeeding would lead to a higher gain in fat.
And finally, the Holy Grail in these studies was one done in 1991.
This study looked at calorie requirements for weight maintenance of anorexics and bulimics. They took anorexics who were 4 weeks into recovery and at 95%-100% of normal body weight vs. bulimics who were 1-4 weeks into recovery and at a normal body weight and compared their caloric intake and weight gain. The results?
After weight restoration, restricting anorexic patients required significantly more calories per day to maintain weight than did bulimic anorexic patients, as measured with corrections for weight, body surface area, and fat-free mass. Previously anorexic normal-weight bulimic patients required significantly more calories per day to maintain weight than never-anorexic normal-weight bulimic patients, as measured with correction for weight but not with the other factors used to correct caloric intake
Now, this study came with some caveats in the conclusion.
Differences in caloric needs between normal-weight bulimic patients with and without histories of anorexiamay depend on the methods used to correct caloric requirements. Body surface area may be the most precise correction factor across different subgroups of eating disorder patients. Elevated caloric requirements, when coupled with reduced food intake, may particularly contribute to relapse in anorexic patients.
Did you guys read that last part? Remember that every time you feel a relapse. There are medical reasons behind these feelings, they are normal.
In conclusion – I was wrong. My metabolism is not permanently screwed up. Neither is yours. Initially we gain back weight that was important for our survival, as shown by how low our metabolism got when we were at our sickest. After that? Our metabolism and body requirements mirror those of people who NEVER suffered through an eating disorder. Who else can benefit from these studies? Yo-yo dieters, chronic dieters, people trying to slowly go into Intuitive Eating…these studies cross a wide range of potential eating issues.
Recovery is possible. It’s a long term uphill battle and never an overnight thing. Give your body time to adjust, your mind time to adjust, and find lots of support and love amongst those around you. You have time to turn your life around, it’s never too late.