Low Carb Diets- Reviewing the Evidence

There is a growing trend in the rise of low carb diets and very low carb (ketogenic) diets across the world.

Frequently we see articles appearing in the press and on social media about the benefits of low carb diets. But what is the evidence? And are they safe?

What are low carb diets?

Low carbohydrate values are poorly defined. Very low carb diets such as ketogenic diets   can vary from 20-50g of carbs per day. Whereas a moderate carbohydrate intake may allow 130g+ per day.

What do carbs do?

Carbohydrates are our main and energy source in the diet. Restricting our carbohydrate to 20-50g a day in the ketogenic diet, our body has to use energy from other sources.
It does this by putting our body in to a metabolic state called ketosis. This is when you generate energy by breaking down fat stores to produce ketones. Ketones will take over as the main energy source for the brain and the rest of the body. Usually ketones are produced at a low and safe level. “This is different to the term ketoacidosis. Which is when ketone levels build up to a dangerous level and can be life threatening. Usually in type 1 diabetes when there is a severe lack insulin available.”

What are the potential benefits?

Weight loss

The truth is that if you take in less energy than you burn- you will lose weight. No matter what dietary approach you choose.
Therefore, it is not surprising to find that there is evidence for weight loss when limiting carbohydrate.
However, it is important to note that scientific literature shows no superiority of a low carb diet over any other diet which results in energy restriction. Such as the Mediterranean diet, low fat diet, DASH diet and vegetarian diet.

Due to the lack of evidence, both national and international guidelines, do not specify an ideal eating pattern.  Instead it’s recommended  we tailor dietary advice to individuals needs and preferences (ADA, DIABETES UK, EASD).  After all, we know that that one size does not fit all!

Blood glucose levels

There is evidence that very-low/low-carbohydrate diets lead to improvements in HbA1c and/or reductions in body weight, but this needs to be interpreted with caution. This benefit is mainly observed in short-term trials lasting six months or less. The effectiveness and safety of the diet has not been examined in the longer term. At time of writing, there is currently no evidence that this approach is more successful in the long term than any other dietary approach. More research is needed to investigate the long term effects of a very-low/low-carbohydrate diet in people with type 2 diabetes.

Are all carbs bad?

There is increasing evidence to show that refined and processed carbs e.g. cakes, biscuits, white bread, white pasta, sugary drinks are linked with poor health outcomes such as obesity, increased risk of diabetes and heart disease. Ideally we do want to be restricting our intake of this type of carbs.
But when it comes to whole grains, it is a different story! Did you know that wholegrains, beans and legumes can have a protective effect on your heart? They can also lower the risk of diabetes, reduce obesity and even help to lower risk the of cardio-metabolic disease and colo-rectal cancer. They are a good source of fibre and B vitamins which help to keep our blood vessels healthy and reduce our cholesterol. This leads us to consider that perhaps a reduction in carbohydrate may be more beneficial than a strict restriction of whole grain carbohydrate.

whole grain carbohydrate


And the fats?

One concern with following  a low carb, high fat diet is the potential increase in saturated and trans fats. However, this is not always the case. Since saturated fats are hidden in all kinds of carbohydrate based processed foods, by cutting the carbs, you may also be inadvertently reducing your saturated fats e.g. cakes, potato chips, fries, biscuits, pastry.

There has been a lot of controversy around saturated fats in the press over recent times. Do they lead to heart disease? Are they truly bad? Like everything, it’s a good idea to have them in moderation and not focus on one single type of nutrient in your diet. Low carb diets- healthy fatsTry to also include some healthy fats in your diet too. That means having more:

  • eggs
  • fish such as salmon
  • cottage cheese
  • avocado




Don’t forget your veggies!

If you choose to follow a ketogenic diet, don’t get hung up on just the proteins and fats. Remember that you can include some non-starchy veggies too. These are responsible for supplying some fibre, vitamins and minerals to your diet.

Are there any risks?

When considering starting a ketogenic diet as an option for weight loss and controlling your blood glucose (if you have diabetes), be cautious that you may be at risk of possible side effects such as the risk of hypoglycemia (abnormal low blood glucose), lack of concentration, and even constipation (as you may be reducing or eliminating healthful fibrous wholegrains, fruit and even vegetables that help you move your bowels). For people with diabetes who are on glucose-lowering medication and insulin, it is encouraged for you to check your blood glucose more frequently and consult your doctor if adjustments to your medication are required.

The biggest negative of the ketogenic diet is its unhealthy focus on ‘good and bad’ foods. The presence or absence of a particular food or food group is not what matters most for your health and your diabetes – it is the whole dietary pattern that does. One that is made up of mostly unprocessed plant foods and which is low in highly processed foods and added sugar.

As a precaution, you should always check with your doctor or dietitian if you have any concerns starting a ketogenic diet.

In conclusion, one size does not fit all when it comes to the ideal diet for managing your diabetes. It is important to have all of the information you require to weigh up the pros and cons and choose the right approach for you.The best weight loss plan is one you can stick with.

#lowcarb #gettingthebalanceright #onesizedoesnotfitall

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