By Rachel Johnson, Ph.D, M.P.H., R.D.
Let’s admit it—we all have little food moments the whole world doesn’t need to know about. Invariably mine occur at night. Once dinner is cleaned up and I’ve worked my way through the dreaded bag of unfinished office work I hauled home, I begin to hear the call of the night kitchen. The other evening, after answering the call, I was lying on the sofa watching a Seinfeld rerun and spooning my way through a bowl of my favorite chocolate-mint frozen yogurt. I realized I was doing exactly what all the diet tipsters warn against. But what’s wrong with nighttime eating? Is food consumed after dark really more fattening than what we eat during the day?
One theory is that our metabolism slows at night, making the calories we eat after the dinner hour more likely to be stored as fat. The data are sparse on the subject. A small study published more than a decade ago examined nine young men and found that the energy cost of digesting a snack at night was 11 percent compared to 16 percent for the same snack eaten in the morning: a difference of a whopping 10 calories for my 200-calorie portion of frozen yogurt—not exactly overwhelming. Most nutrition scientists agree that the effect is so small that it is of little practical significance in the overall control of body weight. So, if a calorie is more or less still a calorie regardless of when it’s eaten, is nighttime eating a problem?
Eating at night does seem to contribute to weight gain among people who are already overweight. In an investigation of more than 2,000 Danish people, night eating was defined as having little or no food at breakfast (called “morning anorexia”) along with consuming at least half the total daily calorie intake after the evening meal. This seems like a bizarre pattern, but I was surprised to learn that as many as 9 percent of the women and 7 percent of the men reported being night eaters. Over six years, the overweight women who were night eaters gained almost 10 pounds more than those who were not. Few facts exist as to why this happens; perhaps, by the light of the refrigerator in a deserted kitchen, we are more prone to letting our guard down.
If the consequences of nighttime eating can be troublesome, particularly for people who are overweight, can eating earlier in the day make a difference? Certainly, the diet gurus advise us not to skip breakfast. Among American women, breakfast eaters are more likely to have a healthy weight than women who don’t eat a morning meal. Champion breakfasters (in comparison to breakfast avoiders) have better nutrient profiles, tend to exercise more and are more apt to report that they try to control their weight.
Consider the possibility that breakfast might influence the rest of the day’s eating choices. A psychologist at the University of Texas recently found, in a study of 867 normal-weight volunteers, that as the day progressed, the time between eating got shorter while the calories per eating session increased. Interestingly, people who ate the most in the morning consumed fewer calories overall compared with those who did most of their eating in the evening.
I’m starting to better understand the pitfalls of my own evening munchies. While a small bowl of frozen yogurt is a perfectly reasonable nighttime snack, during particularly stressful times (including the very holidays I love) I’m more likely to pop a few extra treats, like some of that delectable fudge a colleague has given me, without really thinking about it.
So far nighttime noshing hasn’t been a weight issue for me. In general I read labels, choose smart snacks like fruit or low-fat frozen yogurts, and I’m a long way from eating most of my calories after 8 p.m. But on those nights that the yogurt just doesn’t do it, I am more vulnerable. If you suspect that your own nighttime eating pattern may be a problem, consider your snack choices carefully and, if you don’t already do so, eat a hearty breakfast. I could certainly benefit from eating less at night, which would probably help me wake up hungrier. But I wonder if my Seinfeld reruns would be as fun without the frozen yogurt.
-Rachel Johnson, PhD, M.P.H., R.D. is senior nutrition advisor to EatingWell and dean of the University of Vermont College of Agriculture & Life Sciences.