Negative Energy Balance

Something that comes up a lot in discussions of anorexia recovery is “energy balance.” This topic is often misunderstood, so I’d like to analyze it here.

The short version:

  • Negative energy balance means expending more calories than you consume over some time interval.

  • We know that persistent energy deficits are harmful for people with anorexia, because they lead to weight loss.

  • However, there is some reason to believe that short term energy deficits may be worth avoiding too.

  • I hope researchers will take note; figuring out how energy balance affects recovery seems like low-hanging fruit.

As always: nothing in this post should be treated as medical advice; I am not a doctor; please don’t make health decisions based on information from anonymous people on the Internet.

A simple definition of energy balance is “net calorie expenditure.” That is, it’s the number of calories you consume minus the number of calories you expend. If that number is negative we would say you’re in “negative energy balance.” If it’s positive we’d say you’re in “positive energy balance.”

What the simple definition is missing is time. Energy isn’t an instantaneous quantity; it’s consumed and expended over time. So when we talk about energy balance, we always need to specify a time interval.

Over long intervals, energy balance is closely tied to weight*. In general, if you weigh more on December 31st than you did on January 1st, you were in positive energy balance for the year. If you weigh less, you were in negative energy balance for the year.

We can look at short intervals too. If you skip breakfast, you’ll be in negative energy balance for the morning. During that period you’ll be burning stored energy. If you eat a big lunch, you might be positive energy balance for the afternoon. That will replenish your depleted energy store.

Things get interesting if we look at overlapping intervals. If you eat a big breakfast, you might be in positive energy balance for the morning. But if you then do a hard workout in the afternoon, you might be in negative energy balance for the day as a whole.

Eating disorder researcher Cynthia Bulik once wrote that one of the most perplexing questions about people with anorexia is: “Why is negative energy balance reinforcing for them?” That is, why do people with anorexia seek out negative energy balance?

If you assume the “negative energy balance” here is long term, the answer is obvious: losing weight requires a long term negative energy balance. Isn’t that exactly what people with anorexia want?

That is the popular understanding of the illness, but it’s not really true for many sufferers. Lots of “high functioning” people with anorexia work hard to maintain a stable weight. I was like this myself: by following strict rules for food and exercise, I kept myself just above the “underweight” BMI threshold.

If these long-term sufferers are generally maintaining their weight, we know they’re not in long term negative energy balance. But they still spend a lot of time in negative energy balance: they often work out excessively. Many stretch out the time between meals. Some eat as little as possible during the day and binge in the evening.

Staying in negative energy balance helps people with anorexia relieve anxiety – sort of. Most people feel sluggish and irritable if they miss a meal. People with anorexia feel disciplined and calm. Going into negative energy balance becomes a way to deal with stress. As eating disorder recovery specialist Tabitha Farrar puts it, energy deficits provide “negative state relief.”

The problem is that the anxiety that negative energy balance relieves usually comes from anorexia itself. The illness bombards its victims with intrusive thoughts. It makes them worry that they’ve eaten too much and exercised too little. If they defy it in some small way (like having coffee with milk), it can torture them for the rest of the day. Self-starvation is a trap for people with anorexia – at first it makes them feel better, but over time it leads to a constant stream of bad feelings.

Although most people focus on psychological factors, there are good reasons to believe that long term negative energy (i.e., weight loss) can trigger latent anorexia. Many people report that their eating disorders started after something like a diet or illness. Also, researchers can induce “activity based anorexia” in laboratory animals by putting them into negative energy balance.

I think people who have had anorexia and partially recovered (i.e., “high functioning” people) ought to also be careful with short term negative energy balance. That is, they should think twice before skipping meals (even if they wind up eating more later to compensate) or doing hard workouts on an empty stomach. I suspect that these things interfere with full recovery.

My hope is that research on this subject will help in the development of recovery and maintenance protocols. Are adults in outpatient settings more likely to succeed in recovery if they adjust the timing of their meals and snacks? What’s the best eating schedule for avoiding relapse? I think there’s a lot to learn here.

* A note about the “calories in, calories out” model: People with obesity are frequently told “just consume fewer calories than you expend and you’ll lose weight.“ Similarly, people with anorexia often hear “just consume more calories than you expend and you’ll gain weight.” This is about as helpful as saying “to succeed in business, simply make more money than you spend.” The details about how calories from different foods interact with different bodies aren’t relevant to our analysis here, since we’re concerned with the net result of the energy intake and expenditure process for individuals.