How Late Can I Eat?

Frank is a Skype client from the mid-Atlantic United States.  He has become a great exerciser in our time together and is being very mindful in executing his food program.  He feels better than when he started, but the truth is, he really isn’t losing weight.  Yes, he has stopped gaining and because he is eating better and exercising, he is getting great benefit for his health, however, he wants to and needs to lose weight and it isn’t going very smoothly.  So last week, I asked him what he thinks the problem is.  After thinking about it for a minute or so, he told me that evenings and nights are very problematic for him.  So I asked him to specify.

Frank wakes up early and commutes about 45 minutes to work each day.  When he arrives home, he eats supper and after spending a short time with his family, he often goes out to do some errands or attended a local class.  In our last conversation, he then informed me that he always takes something to eat when he gets home (10:15 p.m.) after his busy evening. I asked Frank if he is actually hungry then, given he has already eaten 3 meals and 2 snacks during the day and without hesitation, he said he is NOT at all hungry—it’s just something he does.  And to make matters worse, he always chooses unhealthy food at that late hour.

There are those who will still insist that a calorie is a calorie not matter what you eat or when you eat it.  success_failureBut research, even going back many years, is starting to tell us a different story.  For now, we are going to delve into the “when” of eating, and in particular, eating late at night and what the possible health and weight gain ramification might be.  Is it possible that late night eating is what is preventing Frank from losing weight and why do I hear this same story over and over again from different clients over the years?

Late Night Eating

Studies tend to show that when food is consumed late at night — anywhere from after dinner to outside a person’s typical sleep/wake cycle — the body is more likely to store those calories as fat and gain weight rather than burn it as energy, says Kelly Allison of the University of Pennsylvania School of Medicine’s Center for Weight and Eating Disorders.  Some animal studies have shown that food is processed differently at different times of day. This could be due to fluctuations in body temperature, biochemical reactions, hormone levels, physical activity and absorption and digestion of food, says Steven Shea, director of the Oregon Institute of Occupational Health Sciences at Oregon Health & Science University.  “The studies suggest that eating out of our normal rhythm, like late at night, may prompt weight gain” and higher levels of blood sugar, which can raise the risk of chronic disease, Allison says.

In a very old study done on a small sample, people were divided into two groups.  They were fed the identical calories but group one eat all their calories in the early afternoon and group two ate the same calories, but at night.  Group one collectively lost weight and group two collectively gained weight.

Thermic effect of food (TEF) is a fancy name for the energy used up as a result of digesting and absorbing a meal. A study published in the American Journal of Clinical Nutrition found that TEF is higher in the morning than in the evening.  Volunteers were given an identical 544-calorie meal at one of three times. In subjects fed at 9 a.m., TEF increased by 16 percent; in those fed at 5 p.m., TEF increased by 13.5 percent; and in those fed at 1 a.m., TEF increased by only 11 percent. So it’s clear that we burn more calories in the morning.  The effect of calories on body composition is also influenced by the size and frequency of meals. For example, a Japanese study found that boxers placed on a six-meals-a-day weight-control diet lowered their body fat percentage significantly more than boxers who ate exactly the same number of calories in just two meals.

Cortisol – The Stress Hormone

Another factor in night eating is the hormone cortisol.  This is the hormone that is integral to proper function of our stress response. (Someone runs into the street right in front of your car and you slam on the breaks—that is cortisol doing what it is supposed to do).  But when we become over-stressed, which at night can be trying stress responseto stay awake against our body’s wishes; that is the over-secretion of cortisol.  Cortisol increases appetite and might also increase motivation in general, including the motivation to eat. Once a stressful episode is over, cortisol levels should fall, but if the stress doesn’t go away — or if a person’s stress response gets stuck in the “on” position — cortisol may stay elevated, and consequently, lead to stress eating.

Frank and I devised some strategies for him to cope with what had become a bad habit.  He now needed to modify a pretty ingrained behavior, but so far, he has been able to do it.  I received an email early this morning telling me that he had to stay up late last night to get some work done and ate nothing!   And since he started being careful about eating at night, his weight has begun to drop slowly and steadily.

For the average person with an average schedule, it is best to set a curfew to finish solid food about 8 p.m. each night.  Yes, there will be exceptions, like a late meal out or a wedding that runs late.  But even in those cases, try to keep the calories down at that hour.  There are also people who have different work schedules and work night shifts.  It is best to consult with a dietician as to how to handle your particular situation.

It’s not just calories—also the timing is a big factor in losing or gaining weight.  Setting a curfew and not eating late will help me keep my weight down, let you sleep better and it will “add hours to your day, days to your year, and years to your life.” 



  1. Margie Cohen-Jackel January 16, 2017 at 9:24 am - Reply

    All very interesting and indeed true.

    But I would like to hear what suggestions you have for me for the following:

    I am hypoglycemic (low blood sugar) and have been since about age 20. I have always been able to manage my blood sugar with diet, that is,eating meals with protein, cutting out all added sugar etc. I am trying mightily to avoid this turning into
    Type II and am managing so far–I am now 63. This is hereditary on my father’s side.

    I DO eat a 0% fruit yogurt every evening before I go to sleep with some nuts, mainly because I am afraid of waking up with a sugar low
    in the middle of the night. Needless to say, blood tests which require 10-hour fasts pre-test are almost impossible for me.

    What is your take on this?

  2. Dvorah Gorman January 16, 2017 at 12:02 pm - Reply

    thanks Allen. I am in my 70’s but want my final stages to be healthy. Devorah G

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