When should you eat if you’re working night shifts?

Ask Dr. Jason Fung

What should you do if you overeat on low-carb high-fat foods? And should you eat between your working hours when working night shifts? And where does the body get its protein from if you’re working out during an extended fast?

It’s time for this week’s Q&A about intermittent fasting and low carb with Dr. Jason Fung:

Low-carb high-fat trigger foods

Dear Jason,

Thanks for helping people and many thanks for intermittent fasting.

Question: I am a lean woman (164 cm, 58 kg – 5’4″, 128 lbs). I eat keto (30 grams net carbs). I overeat on keto because of some trigger foods: nuts, cheese, cream and avocados. This is not an emotional binge. I find it really difficult not to overeat these foods.

Still… these are high-fat foods, what’s the deal with them? Why do they increase my appetite so much? I thought high fat low carb/keto was everything I needed to decrease my appetite…

What’s your theory about these foods? And what do you suggest? Just eliminate them?

All the best,

Dietary fat can increase satiety but not as much as protein. If you think about eating a steak, or a steak with butter, the butter adds a little in terms of satiety, but most of it comes from the steak. Protein is quite filling. It’s really hard to overeat beef, for example. I consider that protein is the most satiating, fat a little less, and refined carbohydrates especially sugar, the least. For example, drinking Coke adds little in terms of feeling full. However, this does not apply to all carbs – a baked potato, for example is very high in carbohydrates but very filling, too. Beans are also very filling.

So, if you know you tend to overeat fatty foods, you may consider changing to something else instead. I don’t think simply adding more and more fat to the diet is necessarily the answer for weight loss. It may work well in some people, but not everybody.

Dr. Jason Fung

Working night shifts

I work night shifts from 11:00 pm to 7:00 am, is it ok if I eat between my working hours?

Luis Alberto

Eating late at night is not ideal, because you get more insulin secretion for the same food eaten earlier in the day. That means for the same meal, you get more fattening effect. The lowest insulin effect is in the morning or early afternoon.

The disruption in sleep is also bad for weight, but there may not be much you can do about it.

Dr. Jason Fung

Weight lifting on extended fast

A person does extended fasting for several days/weeks.

  1. As muscle fibre requires protein for repairing and building, what happens when a person hasn’t eaten for days? Will the body pull protein from unnecessary skin/other tissue?
  2. Would you recommend lifting weights and/or aerobic exercise during extended fasting.


  1. It depends upon you own personal state of health. Yes, your body will pull protein from other places when necessary. Is it healthy? It depends on your own situation. If you are malnourished, then no, this is not good. If you have excess body fat, or protein, then it’s probably OK.
  2. Yes.

Dr. Jason Fung



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  1. Kaliena
    What kind of answer is the one you gave the guy who has to work nights?!!
    Basically you said 'too bad buddy it's hopeless '...what a horrible piece of advice!!! Im done reading this so called "expert"!
  2. Michelle
    I work third shift myself , after reading that I will not be looking to the doctor for advice.
  3. Adam
    B.S. on the night shift answer. The rising and setting of the sun doesn't affect your insulin levels. The hours of waking, and and resting do. If you work nights then your hours of activity are those times and you should shift your meal times to that. Your 8 hours of daytime resting time should be comparable to what a dayshift worker considers their night time activity.
  4. Donna Gibbs
    Fat is fat.... You will digest or keep.it exactly the same any time of the day..... I'm on nights.... I eat smaller meals now and eat at specific intervals.... And I'm stepping up the elliptical.....
  5. Karen Vincent
    I agree the question was not answer. Like whats the best time to eat for a person working a night shift.
  6. Be Cox
    Fir all those years i worked nights and 12 hour nights i never could get a a straight answer. I ate mostly salads when I was working a contract and they had McDonalds in the lobby.I do know eat something lite like a bowel of cereal before i go to sleep. Nothing heavy. and try to get a least 6 hiurs of sleep.Drink a lot of water and not so much coffee. Good luck.
  7. Betty
    I think Dr Fung answered the question in that it is up to Luis as to what time he is willing to eat. The information that Dr Fung was that if Luis wants to eat during hiactual working hours, then the food he eats will cause a higher insulin response than the same food eaten at say 5pm. This gives Luis the choice of eating his meal at work, but having the possibly minor consequence of not having as swift of results as he might have if he had eaten his meals at 5 pm each day. I have worked the night shift as well and have known many long term night shift workers. The successful weight loss ones tell me that they don’t eat at work and instead have their daily IF meal when they get home..a few hours before the go to bed. This mimics the fasting hours of a person who works 7-3 and then eats at 5 or 6 pm. If Luis works 12 hr shifts, then I would suggest eating at the end of 8hrs going into his last 4 hrs or just wait till the end of his 12 hr shift.
  8. Gentiann
    I agree that dr Fung could have elaborated more.
    He may be too busy with other projects. That does not make him less of an expert or a competent doctor.
  9. Josh
    Eating during work hours isn't an issue. The REAL the potential issue is: How well do you handle your carbs? If you're eating meals that contain carbs during your shift and it makes you feel tired, then you'd probably want to opt for protein bars, protein shakes, or high protein meals from home instead so that you can still maintain your energy/focus while managing your hunger. I don't think time of day will ultimately affect weight loss or weight gain. There isn't really consistent evidence. I think how much protein and calories in your diet are MUCH bigger factors worth focusing on for weight management
  10. Jenn C
    I work nights (8 Hour shift). "Breakfast" is about 2 pm, "lunch" about 7pm and "dinner" is during my shift at about 2am.... This is at least 5-6 hours before I go to bed in the morning. Sometimes I just do small snacks/ meals throughout the day and night until 2am and usually what I eat at night is lighter than a regular meal or I'll get sleepy. I realize we night shift workers are off rhythm-wise with sleep and daylight etc, but what on earth does the daylight or dark have to do with how our metabolism works.... What this doctor seems to be saying is that we are still supposed to eat our meals like a 9-5 worker... which is impossible because we would have to cram in all of our food between say, 2pm and 7pm to "not eat late at night". Unrealistic and makes no sense.
  11. 2 comments removed
  12. Stephanie
    I've found these comments offensive.

    If I or anyone else finds Dr. Fung's answer inadequate, let's just ask for more information. Launching these kinds of personal attacks is rarely helpful to anyone. The man is not an 'idiot', nor 'suposidly' a doctor. He's just provided some brief advice/comments instead of a fully rounded, throughly considered answer.

    I see this all the time on diet doctor. People sometimes quite desperate, pouring their hearts out and receive a reply which is over simplified or cuts straight to the point like "keep a food diary, cut out all condiments" or "try fasting" or "you've lost some weight, just keep going".
    This is just the reality of getting busy people to respond to ordinary people's endless questions. They don't have time to write pages of details allowing for alternatives and emotion. But if we would like to know more here's how to ask:

    "Dear Dr Fung, thank you for your above post. I don't feel like you answered the question sufficiently. Please would you elaborate and provide some specific details if you have time?"

  13. 1 comment removed
  14. Damore Yuno
    As a night shift worker being a sleep technician I can tell you, working night shift does affect your metabolism. If you don't like what a specialist told you, look up more information. Try searching circadian rhythm and night shift work. The circadian rhythm is what tells your body when to release hormones and gets your body ready for sleep. Working night shift is basically going against this. Your body is still being told its time to sleep and glands still release the hormones that would normally be released before you go to sleep. Which include increased insulin and the slowing of your metabolism.
  15. 1 comment removed
    I think the doctor is saying that you have to eat on your awake schedule which is third and not between shifts cause he should be in a resting recovery state.
  17. Dr. Davenport
    OMG!!! SERIOUSLY DR. Fung, NO excuses you are providing a public information in your website; You were once a medical student, you were once a resident you know how hard is to work at night, you should have a simple and straight forward answer for Mr. Luis Alberto.

    On behalf of Medical attendings at Loyola Medical Center at Chicago.

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