What is carb intolerance?

"Diabetes and pre-diabetes should really be called carbohydrate intolerance"

Dr. Aseem Malhotra, NHS cardiologist and advisor to the National Obesity Forum

You've probably never heard of it. But carb intolerance is one of the most common food disorders in the world. It's so common that it's likely that you have some amount of carb intolerance. Read on for what it is, how to test for it, and how to reverse it.

The term "carb intolerance" is helpful to describe a range of linked or overlapping medical conditions.

Early stage symptoms Frequently hungry; sleepy after carby meals; hard-to-shift excess body fat; high blood pressure; beer belly. [1]

A 2013 study estimated 67% of men and 57% of women in the UK are either overweight or obese and this is increasing.

Mid stage Diagnosed with prediabetes.

A 2011 study estimated 35% of adults in the UK have prediabetes and this is increasing.

Advanced stage Diagnosed with diabetes mellitus.

A 2016 estimate is that 7% of the UK has a form of diabetes and this is increasing.

These statistics show it is likely that the majority of the population of the UK has some level of carb intolerance. And the problem is getting worse.

What you can do

Fortunately in many people it is possible to reverse the symptoms, with the exception of diabetes mellitus type 1. [2] This requires specialist treatment such as outlined by American diabetic Dr. Richard Bernstein.

Scientists and doctors are currently changing the way they view and treat these diseases. Until the dust settles, we have to take responsibility for ourselves and look at what treatment works. We show a traditional approach here that has helped many people. But everyone is different so you have to find what works for you.

How do you treat an intolerance? You already know the answer: You stop eating what you're intolerant to.

But what do you eat instead of carbs? Do you have to remove all, or are some acceptable? What about nutrition? What about recipes? This has all been answered many times, so first we look at history.

History of low carb in the UK

"My theory is that this [too much carbohydrate] is the fundamental fault with the diets of civilization."

Professor John Yudkin, 1958

We have records for over two hundred years of successfully treating carb intolerance. In 1797 British Army surgeon John Rollo treated diabetics with a low carb diet.

In the nineteenth century, scientists and doctors began to work out effective ways to lose weight. In 1862 British doctor William Harvey developed a low carb diet for obese London undertaker William Banting. Banting successfully lost weight and published "Letter on Corpulence Addressed to the Public". This was popular and low carb diets became a common way to lose weight.

In 1925, diabetic and founder of Diabetes UK, British doctor Robert Lawrence successfully treated diabetics with a low carb diet.

In 1958 the founder of the Department of Nutrition at Queen Elizabeth College in London, British nutritionist Professor John Yudkin published "This Slimming Business", a guide to a nutritious low carb diet.

Professor Yudkin's books were popular and he published an update as "The Sensible Person's Guide to Weight Control" in 1990.

Unfortunately much of this was forgotten or ignored when the high carb, low-fat fad began in the 1970s. This has led to an explosion of carb intolerance. Many of us can improve our health by following the original scientific advice from a time when obesity and diabetes were rare.

The low carb diet

First of all, if you have been diagnosed with prediabetes, diabetes mellitus or have any other condition please consult your GP before changing your diet. You can request personalised low carb treatment under NHS NICE guidelines. If your doctor does not have experience with low carb, consider finding another. The PHC is a growing network of mainly UK GPs and health professionals with low carb experience.

Professor John Yudkin's 1958 diet is a flexible approach founded in the scientific study of nutrition. We know from recent research why this diet works. Modern science does not suggest much change from what Yudkin recommended 60 years ago. Here is an updated version. [3]

  1. Cut your sugar as much as possible. If you have sweet cravings then replace with sweeteners like stevia, erythritol or xylitol instead, but watch out as anything sweet can cause overeating. Natural sugars like honey, agave etc. are still sugar: glucose and fructose.

  2. Keep your carbs under 50g (10 units of 5g) per day if early stage carb intolerant or 25g (5 units) if mid or advanced. Using units of 5g can make it easier to keep track of your total and when cooking.

    You can count all unprocessed meat, fish, eggs, cheese, mushrooms, green vegetables, fats and oils as zero units.

    If you stick with just these almost zero carb foods, you don't need to count anything.

    For everything else, look at the nutrition label to see the amount of carb per serving.

    Here's a way to get a feel for how much carb is in food. Look up the amount of carb per 100g or 100ml on the nutrition label. Divide that number into 500 to get the serving size that gives you one unit. For example: [5]

    Carb per 100g/100ml Amount with one unit (5g carb) Examples
    1 500 8 good, meaty sausages
    2 250 Pot of cream
    3 167 2/5 can of chopped tomato
    4 125 1/5 cauliflower
    5 100 1/5 pint of milk

    If any liquids have more than 5g carb per 100ml, only use in very small quantities, and probably best to skip them.

    Sugary soft drinks and fruit juice are about 11g per 100ml, so that's 7 units per 330ml can. This is all sugar too, so remember rule 1! Tomato juice though is better, having 3g to 4g per 100ml.

    Examples of high-carb food:

    Carb per 100g/100ml Amount with one unit (5g carb) Examples
    15 33 1 cheap, bready sausage
    23 22 1/7 of a potato
    45 11 1/3 slice of white bread
    72 7 7 strands of spaghetti
    100 5 Just over a teaspoon of sugar

    You can see that the low carb diet means very little or no bread, potato, pasta, rice, grains and other starchy food.

  3. Get your nutrition in: protein; vitamins; and minerals. Have two reasonable helpings twice a day from each of the following four groups: (1) cheese, milk (2) meat, fish, eggs (3) vegetables, fruit (4) butter. Remember most modern fruit has been selectively bred by farmers to be very sweet so should only be eaten occasionally. Green leafy vegetables provide similar or better nutrition but without the sugar.

  4. Don't use trans fats or omega-6 polyunsaturated fats such as margarine or manufactured vegetable oils (sunflower, rapeseed/canola, corn etc). Use traditional fats high in monounsaturated or saturated fat such as lard and other animal fats, butter and ghee. Olive, avocado, coconut or other nut oils can be used.

  5. It can take three weeks or more for your body to get used to not having carbs. If you feel lightheaded or fatigued, adding more salt to your food should help. [4]

  6. After three weeks you should find you're less hungry. Your body is now getting most of its energy from fat. If you only eat when hungry now, you should naturally lose weight.

    Listen to your body, and try to tell the difference between craving carbs and real hunger. If you want something sweet but not savory, you're probably not actually hungry. Remember the idea of eat until 80% full, not bursting at the seams.

This diet is similar to the Banting diet in South Africa made famous by Professor Tim Noakes and named after William Banting. Banting is based on the ketogenic diet described by American Professors Stephen Phinney and Jeff Volek.

Try this for two months and see how you respond. It should be an enjoyable diet and result in weight loss and health improvements.

Intermittent fasting

It is not necessary to eat three or more meals per day. Food supplies have not been secure for almost all of the existence of modern humans.

Our bodies can easily cope with not eating for one or more days. If you don't feel hungry, then don't eat. You may find you end up skipping breakfast or lunch or both. This may have health benefits, similar to the low carb diet as it forces your body to burn fat. [6]

If you find you can't go 24 hours without food, then if you don't have any medical conditions this may indicate you have problems burning fat. Try gradually increasing your overnight fast: each day, have breakfast a little later. Eventually replace it with an early lunch. Then gradually make lunch later. Eventually you should be able to last 24 hours between meals.


We all know that to lose weight or for good health it is best to limit or avoid alcohol. If you do drink, then you can count alcohol in your carb allowance as 4g alcohol = 7g carb. Including the sugars in drinks, this means: [7]

Beer Half pint 7 units (35g)
Wine 125ml 4 units (21g)
Whisky 25ml 4 units (18g)

So you can see alcohol uses up your units quickly but gives no nutrition.

Some low carb drinkers' tricks:

  1. Order a half pint of soda (should be free in good pubs) and top it up with the hoppiest beer in the pub; say a new-style IPA (soda first or it explodes). Result: a light, not-too-hoppy beer at half the cost.
  2. Drink wine the old fashioned way. The ancient Romans never drank wine neat. Order a small glass of wine, but in a pint glass and top all the way up with water. It's a legal requirement under the Licensing Act 2003 to offer 125ml, not the larger 175ml or 250ml.
  3. Fresh lime and soda water is free in good pubs.
  4. Pork scratchings and pickled eggs are zero carb and great pub snacks!



A number of recipe books are available and some are cheap or free.


Please email or tweet with any questions and progress reports!


[1] There isn't a formal definition, but "pre-prediabetes" is the idea. Any of a range of conditions such as obesity; idiopathic postprandial syndrome; reactive hypoglycaemia; insulin resistance; metabolic syndrome. Suggestions welcome. Calling it "pre" something implies there isn't yet a problem. This is a failing approach. Instead, decisive lifestyle intervention early on can prevent prediabetes or type two diabetes developing.
[2] Among others, Phinney and Volek's recent paper http://diabetes.jmir.org/2017/1/e5/
[3] Yudkin included margarine because it was cheaper than butter and pre-dated the study of the health effects of trans fats and omega-6 oils.
[4] Natriuresis of fasting.
[5] Nutrition info taken from Tesco's website.
[6] This study showed increased fat oxidation and decreased fasting insulin.
[7] These values are taken from the tables in Yudkin's "This Slimming Business", clearly from calorie equivalence.