The pro’s and con’s of low carbohydrate diets

Lately I have noticed many of my patients have wanted to discuss the credence of low carbohydrate diets. There is certainly a wealth of information of such diets and this has become very topical particularly in diabetes care.

I thought I would take some time to discuss the pro’s and con’s and try to give a balanced view point towards both sides of the argument but it might be a good idea to start with looking into why the argument exists in the first place.

Why low carbohydrate diets at all?

The idea for weight loss is simple. Carbohydrates are one of our primary energy sources. They include foods such as bread, pasta, rice, cereal, potatoes and oats. They also include natural sugars such as fruit and milk sugars known as lactose and also processed sugars such as sucrose.

By reducing them or cutting them out entirely the idea is your body can the turn to its other primary fuel source; fat. This then allows your body to break down fat and thus kick starts weight loss.

From a diabetes perspective, it is the carbohydrates that effect your blood glucose levels and therefore by reducing these it will translate into better diabetes control.

Pro’s of low carbohydrate diets

Weight loss and blood glucose control

In the UK, we typically overeat. With over 60% of adults overweight or obese and this number is on the increase, this is quite clear. Weight gain and inactivity explains the vast majority of cases for type 2 diabetes.

Reducing your carbohydrate intake may not therefore be a bad idea if the place you are starting from is a position of excess. Many of my patients will overeat carbohydrates as they use these foods to bulk out meals and follow them up with a sweet treat afterwards.

This often leads to an excess in calories compared to your body’s requirement and a spike in blood glucose levels if you are suffering with diabetes, type 2 diabetes in particular.

Many forms of carbohydrate are very processed in modern diets. Obvious foods like cakes, biscuits, chocolate and sweets are of course processed and can make managing blood glucose levels tricky, even if you are suffering with type 1 diabetes and are carbohydrate counting effectively.

Processed carbohydrates

However, white varieties of flour, pasta, rice and bread can cause similar spikes in blood glucose levels due to the level of processing of these foods. When harvesting grains they have various different constituents known as wheat, germ, endosperm and bran. During processing it is quite typical for any one or a combination of the germ, endosperm and bran to be removed. This significantly impacts the nutrition and how the grain will be absorbed in the body.

Therefore, for better blood glucose control and a more ‘healthy diet’ it is a better option to opt for more wholegrain varieties of these foods.

The low carbohydrate supporters can often blur the line between between what types of carbohydrates need to be reduced but often it is these processed types of carbohydrates they are referring to. This is therefore not necessarily a bad thing because ultimately it can lead to a more healthy way of eating.

Essential nutrients

Unlike fat and protein, there are no essential carbohydrates that the body cannot make for itself. Fat, has the essential fatty acids omega 3 and omega 6. The body cannot make these on its own and must get these sources of fat from dietary intake.

Likewise, proteins are made up of individual building blocks known as ‘amino acids’, of which some are essential and others are not. Think of a protein as a completed house and the amino acids as the individual bricks used to build it. The body can only get certain amino acids through dietary intake.

Carbohydrates have no such nutrients. Carbohydrate once absorbed is turned into glucose. The body is able to make glucose from both fat and protein as it requires. This in itself produces a two way argument of whether glucose is non essential because we can make it from other sources or whether it is so essential we must be able to produce glucose from non carbohydrate sources.

The answer to this I do not know but it leads us onto a an interesting discussion.

Carbohydrate requirement

Carbohydrates provide energy. They are the primary and preferred fuel for the central nervous system and brain but these can manage with an alternative source, known as ketones, made from fat breakdown, although this is not ideal.

Carbohydrates also provide energy when you are active. As intensity increases during activity, carbohydrate becomes more and more the primary energy source. During lower intensities or rest, fat provides the bulk of energy for the body.

Therefore, if you are someone who is mostly sedentary and doesn’t use a great deal of energy, it is likely your carbohydrate is lower.

Therefore, the argument in this instance may not be for lower carbohydrate diets, but instead the correct amount of carbohydrate for you.

Cons of low carbohydrate diets

It’s just calories

Processed carbohydrates will cause a slightly different hormonal response in your body compared to wholegrain carbohydrates. However, this will not be the difference between weight gain or loss and it won’t be the difference between good or poor diabetes control. Instead, choosing wholegrain varieties is just another tool in your locker to help.

Ultimately, when it boils down to it, the difference between weight gain or weight loss is your overall energy intake compared to your overall energy expenditure. Calories in versus calories out.

Therefore, it doesn’t matter if you create this energy deficit from carbohydrates, fat, protein or alcohol. Carbohydrates get a bad name for reasons described above and also because they are one of the easiest to lose from a meal. A carnivore may not want to reduce the size of their protein source at meal times and so carbohydrates are the obvious alternative.

The evidence is quite clear, for long term weight loss, no one method is particularly better than any other. What is clear however, is an individual needs to make a lifestyle change and be consistent with it.

Cutting out processed food

I’ve yet to come across a diet that endorses eating more cake, biscuits, sweets or processed carbohydrates. When you analyse most diets, what they have actually achieved is significantly reducing the foods which are most likely to lead to weight gan or poor blood glucose control.

How they market such a diet may be different but at the heart of the vast majority of diets, it is the ‘junk food’ which is cut out.

Many people eat carbohydrates and are just fine

There are many people who eat carbohydrates and do not suffer with weight management problems or diabetes. This is because they eat the correct amount of carbohydrates for them.

Athletes include good sources of carbohydrates like fruits, wholegrain and vegetables and remain fit and healthy.

It is carbohydrates in excess which is the problem.

Micronutrient deficiencies

Depending on how far you go with reducing your carbohydrate intake will depend on the level of nutrition you restrict.

Those reducing their intake of processed carbohydrates will likely not be restricting their intake of micronutrients.

However, those completely abstaining from carbohydrates or following very low carbohydrate diets, may be putting their long term health at risk. Wholegrain foods are good sources of iron, B vitamins, fibre and folate. If reducing your fruit or vegetable intake it makes it very difficult for the body to get all the nutrition it requires.  Fruit and vegetables provide many different vitamins and minerals, as well as non nutritive food components such as antioxidants.

Therefore, focusing on only carbohydrates can be quite narrow minded and doesn’t account for the bigger picture of health


There you have some of the pros and cons of following a low carbohydrate diet. In reality, if you have type 2 diabetes, restricting your carbohydrate intake is probably a good thing. It’s a strategy I use with patients and it does help. However, carbohydrates aren’t the problem, it is your body’s inability to deal with them. Therefore, making a broader lifestyle change including healthy eating and exercise is a much better long term strategy.

For more information on this, click her for more articles.

Need more help?

If you need more help or just want a step by step guide and plan to follow, check out our consultancy and programme pages.