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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