How do you add back calories without gaining weight?

Ask Dr. Jason Fung

What can you do about hair loss on low carb or intermittent fasting? What type of oil is best for cooking? And how do you increase your caloric intake without gaining weight?

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

How do your patients reverse hair loss caused by IF and LCHF?


A few days ago you answered another site member’s question by saying that some people do experience hair loss with fasting or or a LCHF diet. You said it is usually reversible. Can you please tell us how that can be achieved? Also do you know what causes it? Could it be a lack of protein in the diet for example, do you think? Thanks.


I don’t know what causes it, but have heard patients complain frequently. Lack of protein should not be a factor as protein intake should be the same in LCHF versus regular diets. Please refer to this article ‘Can Low Carb Diets result in Hair Loss?’ and this post ‘Common Problems‘ for more details.

Dr. Jason Fung

What type of oil is best for LCHF?

I would like to know which oil I should be using for cooking, and which oil for dressings etc. I am trying to find out more about inflammation, so I think this means reducing Omega 6, increasing Omega 3, please can you help?


Most people refer to the omega 3:omega 6 ratio. Ideally, this should be close 1:1, but in modern diets, it tends to be closer to 1:10 due to the heavy use of industrial seed oils. Corn oil, safflower oil, vegetable oils are all man made, heavily processed oils which are predominantly omega 6. The high omega 6 level tends to be pro-inflammatory.

Personally, I suggest people use natural oils – those found in meat, dairy, as well as olive oil (which is cold pressed, and not the processed variety). Personally, I use olive oil and butter mostly. Coconut oil is also good but my kids won’t eat it.

Dr. Jason Fung

How to go upwards of 1500 calories without gaining weight?

I enjoyed your book on obesity & the video on the calorie misconception. If I have been restricting my calories to 1500 for years while me BMR is 1700 and with light activity 1900 cals a day.

I’m currently tracking macros on Myfitnesspal to teach myself to eat keto and this calculates calories as well. Do I just jump in the deep end or gradually increase my calories to just over 1700 to help ‘teach’ my body to burn the right amount?


I don’t pay any attention to calories. The body does not care about calories. It only responds to hormones – chiefly insulin. If your insulin is low, then you are able to access your fat stores for energy. Technically, insulin inhibits lipolysis – that is, insulin stops fat burning. If you can’t burn fat, then you must rely on your food intake for energy, and if you only eat 1500 calories, you will only burn 1500 calories.

However, if you lower insulin, then you can eat 500 calories and take the other 1500 calories from fat, and hey presto – you start to lose body fat as your body starts to burn 2000 calories. There is an overlap, for sure, between calories and insulin, but it is not one to one. Refined carbohydrates and sugars are the worst for insulin and natural fats are the best.

Dr. Jason Fung



Intermittent Fasting for Beginners

Earlier Q&A

Intermittent Fasting Q&A

Q&A videos

Top Dr. Fung videos

More with Dr. Fung

Dr. Fung has his own blog at He is also active on Twitter.

His book The Obesity Code is available on Amazon.

The Obesity Code

His new book, The Complete Guide to Fasting is also available on Amazon.



  1. Niki
    Low potassium causes hair loss, as far as dietary needs go.
  2. Trish Zartman
    I am Diabetic and take a very small amount of basal insulin daily. Without it my sugars are not coming trolled but with it have beautiful control. How do I lower insulin to burn fat without running the risks of HHNK or DKA?
  3. Jo
    Re Hair Loss: take heart, it's proof things are changing!
    I had this problem about 6 months after commencing Keto... it did resolve after a few months but I've never been able to find out why it occurred. Until now.
    Dr Ron Rosedale gives a very detailed answer in a recent interview with Jimmy More... I won't try to explain the cascade of hormonal changes that occur when one changes to low carb, but the point is that Rosedale is very, very aware of the exact mechanism behind hair loss and this is pretty normal and indicative of the fact that the diet is working on a hormonal level... and it will resolve. I'm a very big Dr Fung fan but "I don't know... (it's not unusual)" doesn't cut the mustard. The science is out there; let's keep trying to uncover it!

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