Are low-carbohydrate diets effective with weight loss?

Low carbohydrate diets for weight loss were first introduced in 1860, but have gained a lot of popularity in recent years. A low carbohydrate diet is a diet that contains less than 26% of all its calorie intake coming from carbohydrates. One popular type of low-carbohydrate diet is the ketogenic diet, which restricts carbohydrate intake to less than 50 g per day. Several studies have shown that low-carbohydrate diets help with weight loss. Some believe that this is due to its increased consumption of high-fat and protein foods, which increase satiety, reduce hunger and overall calorie intake. Another theory is that low—carbohydrate diets increase metabolism and the production of ketone – a chemical that the liver produces when it breaks down fat so that it can be used for energy when little or no carbohydrates are present in the body. However, these theories remain controversial.

Restricting carbohydrate intake, however, can bring many concerns. For example, several studies have shown that a low carbohydrate intake and a higher fat intake can lower life expectancy as they can increase the risk of cardiovascular disease. Carbohydrates are also the main source of energy, especially during intense training. When we consume carbohydrates, it is broken down into glucose into the body for use of energy. Unused glucose is stored as glycogen (stored energy) whilst a small amount (around 10-15%) of carbohydrate is expanded as heat. Low glycogen stores can lead to reduced energy and fatigue, and reduce performance.

Carbohydrates are not only a good source of energy, but they help preserve protein from being used as energy, allowing it to instead be used on tissues inside the body such as muscle repair and building new muscle cells. In contrast, if protein intake is used as energy due to poor carbohydrate intake, it can lead to muscle atrophy (muscle loss). Muscle is crucial to increasing our metabolism, meaning that we burn more calories during rest. The more muscle we have, the higher our metabolism will be, and the easier it will be to lose fat. The body can store about 500 g of glycogen (for more information about how glycogen is stored, see the blog: An Introduction to Carbohydrates). Any excessive carbohydrate intake, especially those with a high Glycaemic Index, will cause blood glucose levels to rise. This triggers the pancreas to release the hormone insulin, which converts carbohydrates to fat.

Eating the required amount of carbohydrates, without exceeding, and eating low Glycaemic Index foods will help keep the insulin level low. Weight loss should not be about cutting down a specific nutrient. It should be planned around cutting down overall calorie intake. Reducing approximately 10-20% from your daily calorie expenditure will help you lose weight as you will create a negative calorie balance (you burn more calories than you consume). Just a 10-20% cut can help you lose up to 0.5 kg per week without causing feelings of hunger and lethargy.

Thanks for reading, and as always stay fit!

Coach Darren

References

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Hall, K. D., Bemis, T., Brychta, R., Chen, K. Y., Courville, A., Crayner, E. J., ... & Yannai, L. (2015). Calorie for calorie, dietary fat restriction results in more body fat loss than carbohydrate restriction in people with obesity. Cell metabolism, 22(3), 427-436.

Ludwig, D. S., & Ebbeling, C. B. (2018). The carbohydrate-insulin model of obesity: beyond “calories in, calories out”. JAMA internal medicine, 178(8), 1098-1103.

Nordmann, A. J., Nordmann, A., Briel, M., Keller, U., Yancy, W. S., Brehm, B. J., & Bucher, H. C. (2006). Effects of low-carbohydrate vs low-fat diets on weight loss and cardiovascular risk factors: a meta-analysis of randomized controlled trials. Archives of internal medicine, 166(3), 285-293.

Noto, H., Goto, A., Tsujimoto, T., & Noda, M. (2013). Low-carbohydrate diets and all-cause mortality: a systematic review and meta-analysis of observational studies. PloS one, 8(1), e55030.

Oh, R., & Uppaluri, K. R. (2020). Low carbohydrate diet. StatPearls [Internet].