Is a low carb diet healthy?

What is a low carb diet?

Low carbohydrate diets have been around for several decades, however as of late they have surged in popularity. In fact, with the rise of overweight and obesity, the public is eager to find solutions to their expanding waistlines. 

There is no governing authority that regulates or defines what constitutes a low carb diet. However, for context, the typical western diet provides 50% of energy from carbohydrates, 35% of energy from fat and 15% of energy from protein. In comparison, a high fat low carb diet can provide 60% of energy from fat, 10% from carbs and 30% from protein. 

The low carb pioneer

But perhaps the most famous low carbohydrate diet, considered the pioneer of the low carb movement, is the Atkins diet. 

In 1972, Dr Atkins released his book titled the Dr Atkins’ Diet Revolution which sold millions of copies worldwide. The Atkins diet is divided into four steps. Firstly, there is a two-week induction period during which you restrict carbohydrates to less than 20 grams/day. The diet recommends moderate protein intake from animal foods such as beef, chicken and eggs, and fat intake is unlimited. Moreover, during this phase, you are not allowed bread, grains, fruit and starchy vegetables. Further, you are not permitted dairy products with the exception of cream, cheese and butter (due to their low carb, high fat content). 

Throughout the following stages, carbohydrate restriction is eased until the individual can determine the amount of carbohydrate required to maintain weight loss. This level varies widely amongst individuals and could be anywhere between 25 grams/day up to 90 grams/day depending on body weight, physical activity and other factors. Moreover, the diet encourages followers to check their urine for ketone bodies to ensure they are in ketosis.(1)

Ketosis...

When following a low carb diet, one of the typical bodily consequences is ketosis. Ketosis refers to a bodily process that occurs when our carbohydrate intake is limited. In fact, when our body is faced with low carb intake, it utilises our glycogen stores which are broken down into glucose to use as fuel. The liver and muscles are the primary glycogen stores in the body. However they are finite stores and within 24 to 48 hours of dietary carbohydrate restriction, they become depleted. 

Furthermore, a characteristic of glycogen is that it binds to water. Therefore, this explains why during the first week of a highly carb restricted diet such as Atkins, many people achieve “weight loss”. However, this is due to water loss as opposed to fat loss. Loss of glycogen and water does not truly reflect weight loss because once the diet ends, these stores will be replenished. However, if the diet continues and we do not replenish glycogen stores, the body starts to utilise its fat stores. Therefore, our body releases fatty acids  into the bloodstream and the liver utilises them to produce energy. 

And ketone bodies

When the liver partially oxidises fatty acids, it produces a compound called acetoacetate which is then converted into b-hydroxybutyric acid. Together, we refer to these compounds as “ketone bodies”. Our kidneys filter ketone bodies causing an increased loss of sodium and water. The maximum amount of carbohydrates required to induce ketosis varies between individuals. However, typically it equates to less than 20% of total energy intake. 

There are very few studies observing the long-term health effects of ketogenic diets. However, commonly reported side effects include dehydration, gut issues, vitamin deficiencies and low blood sugar. Moreover, long-term ketosis leads to increased levels of uric acid in the blood. Long-term high levels of uric acid could be linked to kidney and joint complications.(2)

Related reading

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• 5 healthy living myths you need to know about