Does skipping breakfast lead to a higher risk of type 2 diabetes?

Ask Dr. Jason Fung

It’s time for this week’s Q&A about intermittent fasting:

  • Can you get low blood sugar during fasting?
  • Does skipping breakfast lead to a higher risk of type 2 diabetes?
  • Does protein powder raise blood glucose?

Dr. Jason Fung is one of the world’s leading experts on fasting for weight loss and diabetes reversal. Here are a his answers to those questions and more:

Can you get low blood sugar during fasting?

Hello Dr. Fung, I am prediabetic, and I have had great success with fasting in helping me to lose weight, and to lower my HbA1c (when last checked it was at 5.9).

I am a menopausal woman and am 53 years old, and also have mild case of Hashimoto’s disease (my antibody count when last checked was 15). I take levothyroxine, and liothyronine, plus estrogen, and progesterone the first 10 days of the month. I also mainly follow a ketogenic diet.

I am a huge fan of you, Jimmy Moore, Dr. Nally, and this website. When I go on longer fasts (7 days) by about day 5, I start to experience low blood sugar and have measured my levels at 48 mg/dl (2.7 mmol/L). Is there anything I can do to avoid having low blood sugar episodes?

I have done two 7-day fasts. The last time I only drank water and herbal tea the first 3 days, then I started having a cup of broth or two each day. I also supplemented with a teaspoon of Himalayan pink salt each day, as I was concerned about my electrolytes. I started the fast at 168 lbs (76 kg), and I am 5’7″ (170 cm). I finished at 161 lbs. and then went back up to 163 lbs (73 kg).

I really enjoy fasting and have a family history of diabetes (both parents), and cancer (father), so I really want to continue doing longer fasts. I understand that you can’t give specific medical advice, but I am hoping that you can talk about experiencing low blood sugar while fasting in a general way since you have fasted such a large number of people.

Thank you in advance for any help you might offer,

Blood glucose is supposed to drop while fasting. However, you are not supposed to have symptoms, since most of the body is now powered with fat and ketones. The body has compensatory mechanisms to produce glucose from stored glycogen and fat called ‘gluconeogenesis’.

Symptoms of hypoglycaemia include shaking, sweating and disorientation. Occasionally, people do notice some mild symptoms. There are certain people who do notice symptoms and should generally stop fasting. If you would like to continue, you may build up fasting slowly – going longer and longer until your body gets ‘used’ to the gluconeogeneis.

There is also a disease called ‘reactive hypoglycaemia’ where people develop symptoms after eating.

Dr. Jason Fung

Does skipping breakfast lead to a higher risk of type 2 diabetes?

If you routinely skip breakfast, you may be headed for trouble, says Leah Cahill, PhD, of the Harvard School of Public Health. One of Cahill’s studies found that women who skipped breakfast regularly had a 20% increased risk of developing type 2 diabetes.

Another of her studies — this one in men — linked going without a morning meal to heart disease. “Our bodies need to be fed food regularly in order to maintain healthy levels of blood lipids such as cholesterol, hormones such as insulin, and normal blood pressure,” Cahill says. “As we sleep all night we are fasting, and so if we regularly do not ‘break fast’ in the morning, it puts a strain on our bodies that over time can lead to insulin resistance, type 2 diabetes, and blood pressure problems.”

From this web page:


Almost all breakfast studies that show a benefit were sponsored by the food companies. Almost all breakfast studies not funded by food companies showed no benefit to breakfast eating. In fact, the studies on breakfast eating are so bad and full of conflicts of interest, an entire paper was written to demonstrate how to distort evidence called ‘Belief beyond the evidence‘. So be very careful. People tell you that ‘studies’ show that eating breakfast will make you healthy, wealthy and be more attractive – it doesn’t make it true.

The other statements you quote here make absolutely no sense. It simply sounds made up. Our body needs to be fed regularly to stay healthy? Where is the evidence or even common sense in that? Does that hold true even if severely overweight and diabetic?

How about ‘fasting strains our body leading to type 2 diabetes?’ Where is the evidence? Fasting lowers blood glucose and insulin, which, if you do it all the time, will lead to high glucose and insulin? Are you serious?

Dr. Jason Fung

Does protein powder raise blood glucose?

Does protein powder made from raw sprouted organic grains, legumes, and seeds raise blood glucose?


No, protein does not raise blood glucose, but it may raise insulin. In general, I advise eating natural whole foods. This does not include protein powder. So if you want to eat organic legumes seeds and sprouted grains, then great. But I would avoid ground up, processed protein powder that claims to be healthy.

Dr. Jason Fung



Intermittent Fasting for Beginners

How to Reverse Type 2 Diabetes – The Quick Start Guide

Earlier Q&A sessions with Dr. Fung:

Many more questions and answers:

Intermittent Fasting Q&A

Read all earlier questions and answers – and ask your own! – here if you are a member:

Ask Jason Fung about intermittent fasting and type 2 diabetes – for members (free trial available)

Q&A videos

  • Is low carb bad for exercise?
  • Is low carb bad for the kidneys?
  • Everything in moderation?

More Q&A videos (for members) >

Top Dr. Fung videos

  • Diet Doctor Podcast #64 with Jason Fung
  • Part 8 of Dr. Jason Fung's diabetes course
  • The essential problem with type 2 diabetes

Full IF Course (for members) >

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.


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