Weighing the benefits and risks of the popular low-carb diet.
A buzzword in weight loss today, the ketogenic diet has been touted as a quick way to shed kilos, improve heart health and control diabetes. What began as a treatment for children with hard-to-control epilepsy in the 1920s has been gaining momentum of late.
But this wildly popular diet is also controversial as it tips the traditional balanced food pyramid. Instead of carbohydrate forming the bulk of one’s calorie intake, it drastically restricts daily carbohydrate consumption to between 20g and 50g (less than a bowl of rice), and replaces it with protein and fat.
When the body’s first source of energy – carbohydrate – becomes unavailable, it then taps into the 500g of glycogen – a form of glucose that serves as energy storage – stored in the liver and muscles. Once that too is depleted, it turns to fat stores.
“With a lot of weight loss attempts, the body fights back with hunger-adaptive hormones, which makes us want to eat more. That is why people regain weight. However, when your body breaks down fat, ketones are produced. These counteract hunger hormones and suppress hunger pangs,” said Dr Tham Kwang Wei, Senior Consultant, Department of Endocrinology and Director at the LIFE Centre, Singapore General Hospital (SGH).
Short-term studies have shown that people on this diet lose weight faster initially – an average of 7 per cent of their weight in six months – as compared to other low-fat diets. This can have a positive psychological effect on many dieters.
One problem, though, is people may over-indulge in processed meats like sausages or fatty cuts of meat, when they should go for lean types like fish and chicken, pick poly- and monounsaturated fat such as olive oil and avocado, and complex carbohydrates such as quinoa and oats.
A diet high in saturated fat has been shown to increase the risk of heart disease, a low-fibre diet increases the risk of cancer, and a high-protein diet of meat and dairies has negative long-term effects on the kidney.
Moreover, patients with multiple health problems such as kidney failure, poorly controlled diabetes, or those taking medications like diuretics should consult a doctor before starting this diet. A very-low-carbohydrate ketogenic diet can lead to dehydration, low blood pressure and the worsening of renal function, Dr Tham said.
“The initial phase of a very-low-carbohydrate ketogenic diet leads to diuresis [loss of water] and the loss of potassium and magnesium. While the water loss leads to the initial rapid weight loss and drop in blood pressure, this may lead to dehydration, which may in turn lead to worsening of kidney function in people taking diuretics or who have kidney failure. The low-blood potassium and magnesium can also predispose the susceptible individual to cardiac arrhythmias, muscle cramps and weakness,” she said.
Diabetic patients may benefit from the drop in blood sugar levels and overall improvements in glucose control. “However, patients on medication and insulin who suddenly go on a low-carbohydrate diet may experience hypoglycemia [low blood sugar], which can be dangerous. Medications may need to be either pre-emptively reduced or blood sugars and pressure be closely monitored,” she added.
Dieters may also lack important nutrients like vitamin B when they cut out carbohydrate or grains. So a multi-vitamin supplement is necessary.
When these guidelines are followed, the ketogenic diet is generally safe for most dieters in the short term. Whether such a diet is safe if followed over a long period is unclear as longer-term studies on its benefits and effects are yet unavailable.
To sustain weight loss for long-term health benefits, Dr Tham suggests a slow transition period of reintroducing some complex carbohydrates, learning new healthy eating habits, and exercising regularly to reduce sugar levels and hunger pangs.
“The best [dietary] intervention is a sustained one with both short-term and long-term benefits,” she said.