'Carbohydrate' or 'Carbs' are buzz words in the fitness and diet universe. Weight loss and diet theories have centred around this food group, claiming notions such as 'cutting carbs leads to immediate weight loss' or 'consuming carbohydrates causes bloating and weight gain'. The demonising of any food, let alone food group, can be extremely dangerous to one's health and mental relationship with food. In this blog post, I will explore why 'cutting carbs' has captured the diet industry and the scientific evidence behind carb-free diets such as the keto diet.
The primary discussion surrounding carbohydrates is that of weight. Carbohydrates are said to the secret to weight loss and many fitness influencers and diet industries have created books and diet plans involving the partial or entire removal of carbodhyrates from the diet. In reality, there is no evidence to suggest weight gain is caused by a single food group. Weight gain is the cause of an energy imbalance (i.e. more calories consumed than burnt), medical issues (for example., kidney disease or medication) or lifestyle issues (for example., reduced mobility).
Carbohydrates are extremely vital to our health and they should make up a good portion of our meals and snacks. They provide us with a variety vitamin Bs, the preferred energy source for our brains and bodies. During long periods of physical activity our body relies on our carbohydrate stores, hence the term 'carb-loading' prior to extreme exercises like marathons. In addition, carbodhyrates, particularly wholegrain or brown versions, are a great source of fibre thereby aiding our digestion and bowel movements.
With such incredible health benefits it begs the questions, why remove carbohydrates from the diet? As mentioned above, there have been claims of weight loss and health benefits associated to the limiting or removal of carbohydrates from the diet. One running hypothesis indicates that lowering carbohydrate intake also lowers insulin levels which affect our bodies fat-storing potential and increases cardiometabolic function (a fancy way of saying we burn more calories). In addition, when compared to other dieting methods such as low-fat diets, restricting carbodhyrates is associated with higher levels of weight loss. Due to the lowering of insulin levels, lower carbohydrate diets have been explored as treatment methods for patients with diabetes. However, a recent systematic review and meta-analysis did not find any evidence to suggest this was a safe, satiating or effective strategy, particularly when used for over 6 months. Another hypothesis in favour of low carbohydrate diets suggests that protein and fat food sources are able to keep the body satiated which reduces the feeling of hunger and therefore overall calorific intake. However, it is important to note, this feeling of being satisfied in high protein-fat diets is largely coming from protein intake alone as fat is one of the least satiating food groups. Further studies [1,2] have similarly concluded there is not enough evidence from studies to make conclusive arguments for or against low carbohydrate diets. While low carb diets do initially lead to greater weight loss in the first 6-12 months, in comparison to other dieting techniques, there are remaining concerns around the safety and long-term sustainability of these diets. Sustainability refers to the ability of an indivdual to maintain this diet for a long period of time. While studies show low-carb diets are effective within the first 6-12 months, there is some question as to whether a person can remove carbohydrates from their diet for longer durations. Food is not only fuel but there are social and cultural elements to eating too. Will you truly be able to never have a sandwhich again, or a piece of cake for a celebration? In addition, there are concerns that becoming obsessed with removing food items or groups from one's diet can lead to disorders such as ARFID or orthorexia. Our mental health must be considered a priority as much as our physical health when undertaking any extreme diets.
One dieting technique associted with both rapid weight loss and health concerns is the keto diet. In the keto diet, carbohdyrates are extremely restricted (some dieters even go as far as restricting fruit and vegetable intake). The idea behind this diet is to induce a natural state in our body known as ketosis. During ketosis, our glucose stores cannot be replimished as we are not eating enough carbodhyrates. Therefore, our liver begins to make ketones and our body begins to draw on these ketones and our fat stores for energy. This is thought to contribute to rapid weight loss during the first few months of ketosis. In addition, our water weight (how much water our body can hold) is also reduced due to the limited carbodhyrates in our diet. However, the ability to put our bodies into metabolic ketosis purely using diet is still in question. A recent review indicated that there was no evidence or low quality evidence for the safety of the keto diet in patients. This included patients with type 2 diaetes which the keto diet is thought to assist. Results were also controversial regarding increased mortality and cardiovascular risks in low carbodhyrate diets. Some studies indicate that low-carb diets lead to small increases in LDL cholestrol which is associted with increased cardiocvascular risks. However, other studies show no increase in LDL and infact argue that after long durations, low-carb diets help improve HDL cholestrol which is associated with reducing cardiovascular risks [1,2,3,4]. Low-carb diets such as keto are often the source of kidney concerns due to the increase in protein being consumed. For individuals with normal and healthy funcitoning kidneys, there is no research suggesting this high protein intake will affect kidney function. However, for those with a history of kidney problems, the undertaking of low-carb, high-protein diets should be discouraged.
Finally, individuals undertaking the keto diet should be made aware of the symptoms experienced when removing carbohydrates from the diet. The keto diet can induce a state commonly referred to as the 'keto flu' within the first few weeks of commencing the diet. Symptoms of this 'flu' include headaches, brain fog, low energy levels and diziness (perhaps caused by the lack of the brain's preferred energy source), nausea, gastrointestinal problems, alterations to heartbeat and reduced energy. Therefore, given the mixed evidence base and safety concerns, healthy individuals and individuals with health conditions should be extremely careful when considering undertaking this diet.
The origins of the keto diet lie in the treatment of epilepsy and this has been highly successful. While the keto diet and other low-carb diets remain a controversial in regards to safety, cardiovascular risk and long term sustainability, they may still prove useful for other disease treatments. For example, there is promising research on the ketogenic diet to prevent and treat Alzheimer's disease, cancers and PCOS. This review highlighted how the keto diet's reputation for weight loss and safety concerns may hinder progress for its use in other health treatments. Despite, conflicting research on the use of low-carb diets for weight loss, I do not believe this should deter future research or doctors from exploring the use of food and diet as a potential prevention and treatment for diseases. This is largely due to the ability of patients undertaking this diet to be well monitored and advised in these settings. In contrast, people undertaking the diet for weight loss at home are often left to their own research and not under supervision or professional instruction. In addition, some diseases such as Crohn's Disease or Coelic Disease can lead to extreme bloating or stomach pain after eating foods within the carbodhyrate group. If you are concerned about these symptoms it is important to not self-diagnose but instead see a doctor or dietician who can help determine if you have a dietary disease/intolerance. I urge any readers to not cut out entire food groups or food items without medical direction and supervision.
Overall, given the current evidence base, as a nutritonist I would err on the side of caution when undertaking drastic diets, whether keto, low-carb, or low-fat. Without sufficient evidence for the safety and effectiveness of these diets I would urge people to steer away from restrictive diets. I believe all foods and food groups have a central part to play in the maintence of our health. In addition, I would always be in favour of creating long-term, healthy habit changes such as increasing daily movement and balancing meals instead of dieting and calorie restriction. However, if weightloss is a priority for your health or you are experiencing health concerns it is vital you first seek the support and advice from a professional prior to self-dianosis or treatment. Should a professional recommend trying a diet restricting certain foods or food groups, cardiovascular monitoring and supervision from the professional should be maintained.
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