Whether it is the Atkins, Dukan or the ketogenic diet – the popularity of low or non-carbohydrate diets is consistently rising. Just looking at Instragram alone, the number of hashtags for #lowcarb is almost 9m, while #lowfat has just over 1m. Fat and protein are enjoying celebrity status in today social-media society (#protein is at a whopping 19m hashtags and #fat at 11m) while carbohydrates seem to be avoided like the plague (some lonely 0.2m hashtags for #carb). However, restricting the intake of carbohydrates is not only relatively unfeasible, but it can also be relatively dangerous as well as not as effective as may be assumed.
Given the fact that carbohydrates include vegetables, fruits, grains, legumes and pulses, and that sugar is also found in dairy in the form of lactose, it is, in fact, relatively difficult to eliminate their consumption completely. A “carb-free” diet therefore usually refers to a diet limiting starchy carbohydrates, such as grains and potatoes.
Such diets are thought to be effective tools for weight loss. The truth is, they probably are, in the very short term. This is mainly a result of a reduction in total body water content – a common result in the first one or two weeks of restricting carbohydrate intake. Water bound to carbohydrates is lost, reducing water retention in the body.
Additionally, when carbohydrate intake is restricted, water is lost via the mobilisation of glycogen stores in liver and muscle. Each gram of glycogen is mobilised with approximately 2g of water. The liver stores approximately 100g of glycogen and muscle has 400g of glycogen. Mobilisation glycogen stores result in a weight loss of approximately 1 kg. However, as soon as carbs are re-introduced into the diet, the water weight will be gained back and the visual results from the low-carb diet will be reversed.
Longer-term weight loss from carbohydrate restriction mainly stems from the fact that eliminating a whole food group restricts a variety of food choices, thus resulting in a caloric deficit, which is needed for weight loss. However, this is likely to lead to social isolation and has been found not to be sustainable over a prolonged period. In fact, long-term follow-up studies document that the majority of individuals in diet-intervention studies regain virtually all of the weight that was lost during treatment.
Not only are diets not necessarily successful in the long term, restricting carbohydrates for a longer period of time can have a substantial negative impact on overall health. Carbohydrates provide fibre (necessary for a healthy gut), essential vitamins and minerals, and phytochemicals (independent plant-based compounds that are very small by themselves, but can, in aggregate, improve health in a variety of ways). More information on nutritional benefits of whole grains can be found in the article Grains – Friend or Foe. Low-carbohydrate diets have been found to lead to constipation and higher risk to nutrient deficiencies. They are also likely to affect mood, energy level and mental capacity, as brain cells require glucose (the simplest form of carbohydrates) as it is the only form of energy they can use.
Aside from missing out on a number of important micro-nutrients, being on a low carbohydrate diet for a long time can severely disrupt the hormonal system. Consequences include elevated cortisol levels, which can result in the body holding on to fat reserves. Another hormone that can be affected is thyroid hormone T3, which is important for metabolic regulation, particularly blood glucose management. Prolonged fasting and/ or restricted carbohydrate intake has been associated with drops in T3 hormone, which can have severe effects on overall health and energy levels.
Females especially can experience severe endocrine consequences from prolonged carbohydrate restriction. It can cause hypothalamic amenorrhea, which can lead to anything from irregular periods to a complete shut-down of the reproductive system.
Especially at this time of the year, when there is a push for diets and weight loss programmes, it’s important to be aware, not only of the questionable efficacy, but more importantly of the potential dangers of restricting certain food groups. Rather than focusing on what to restrict, it’s emotionally and physiologically easier and more sustainable to focus on the addition of nutrients to the diet that will make you feel good and that promote health and enhance the body’s function