In the world of weight-loss diets, low-carbohydrate, high-protein eating plans often grab attention. The Paleo, South Beach, and Atkins diets all fit into that category. They are sometimes referred to as ketogenic or "keto" diets.
But a true ketogenic diet is different. Unlike other low-carb diets, which focus on protein, a keto plan centres on fat, which supplies as much as 70-90% of daily calories. And it's not the type of diet to try as an experiment. The keto diet is primarily used to help reduce the frequency of epileptic seizures in children. While it also has been tried for weight loss, only short-term results have been studied, and the results have been mixed. The long term impact is not well studied as most of people are not able to continue it over the years.
How does it work?
The keto diet aims to force the body into using a different type of fuel. Instead of relying on sugar (glucose) that comes from carbohydrates (such as grains, legumes, vegetables, and fruits), the keto diet relies on ketone bodies, a type of fuel that the liver produces from stored fat.
Burning fat seems like an ideal way to lose pounds. But getting the liver to make ketone bodies is tricky:
l It requires that we deprive ourselves from carbohydrates, fewer than 20 to 50 grams of carbs per day (keep in mind that a medium-sized banana has about 27 grams of carbs).
l It typically takes a few days to reach a state of ketosis.
l Eating too much protein can interfere with ketosis.
What does someone eat?
Because the keto diet has such a high fat requirement, followers must eat fat at each meal. In a daily 2,000-calorie diet, that might look like 165 grams of fat, 40 grams of carbs, and 75 grams of protein. However, the exact ratio depends on the particular needs.
Some healthy unsaturated fats are allowed on the keto diet - like nuts (almonds, walnuts), seeds, avocados, tofu, and olive oil. But saturated fats from oils (palm, coconut), lard, butter, and cocoa butter are encouraged in high amounts.
Protein is part of the keto diet, but it doesn't typically discriminate between lean protein foods and protein sources high in saturated fat such as beef, pork, and bacon.
What about fruits and vegetables? All fruits are rich in carbs, but you can have certain fruits (usually berries) in small portions. Vegetables (also rich in carbs) are restricted to leafy greens (such as kale, Swiss chard, spinach), cauliflower, broccoli, Brussels sprouts, asparagus, bell peppers, onions, garlic, mushrooms, cucumber, celery, and summer squashes. A cup of chopped broccoli has about six carbs.
A ketogenic diet has numerous risks. Top of the list: it's high in saturated fat. Dietary guideline recommends to keep saturated fats to no more than 10% of our daily calories because of the link to heart disease. And indeed, the keto diet is associated with an increase in "bad" LDL cholesterol, which is also linked to heart disease.
Other potential keto risks include these:
Nutrient deficiency. "If someone not eating a wide variety of vegetables, fruits, and grains, we may be at risk for deficiencies in micronutrients, including selenium, magnesium, phosphorus, and vitamins B and C.
Liver problems. With so much fat to metabolize, the diet could make any existing liver conditions worse.
Kidney problems. The kidneys help metabolize protein, and the keto diet may overload them. (The current recommended intake for protein averages 0.8 to 1.2 per kg body weight per day.
Constipation. The keto diet is low in fibrous foods.
Fuzzy thinking and mood swings. The brain needs sugar from healthy carbohydrates to function. Low-carb diets may cause confusion and irritability.
Those risks add up - so make sure that you talk to a registered dietitian before ever attempting a ketogenic diet.
What about the other diets?
The popular low-carb diets (such as Atkins or Paleo) modify a true keto diet. But they come with the same risks if you overdo it on fats and proteins and lay off the carbs. Theories about short-term low-carb diet success include lower appetite because fat burns slower than carbs. "But again, the impacts on long term still unknown. And eating a restrictive diet, no matter what the plan, is difficult to sustain. Once, someone resume to a normal diet, the weight will likely return.
The writer is a nutritionist and working for an NGO.
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