A ketogenic diet is one that comprises high fat, moderate protein and low carbohydrate intake.
Carbohydrate foods provide glucose, the main source of energy for all cells in the body. When carbohydrate intake is restricted, the body first uses stored glucose from the liver and temporarily breaks down muscle to release glucose. If this continues and stored glucose is fully depleted, usually after 3-4 days, blood levels of a hormone called insulin decrease, and fat becomes the first and primary source of fuel. The liver breaks down the fat into an alternative source of fuel called ketones.
When ketone bodies accumulate in the blood, the body is in a state of ‘ketosis,’ a metabolic state in which ketones become an important source of energy for the body and brain.
On a ketogenic diet, only 20g to 50g of carbohydrates per day or less is consumed. As an example, 50g of carbohydrate is equivalent to 2 slices of bread and a banana. Generally, a suggested ketogenic diet looks like an average of 70-80% fat from total daily calories, 5-10% carbohydrate, and 10-20% protein. Eating too much protein can prevent ketosis.
The diet is often considered and recognised for weight loss. It has become part of the low carbohydrate diet trend that started in the 1970s with the Atkin diet. Other diets that have followed on from this trend include the Atkins diet, Paleo diet and South Beach diet. These all involve high protein intakes.
The ketogenic diet sets itself apart as it is high in fat, typically 70% to 80%, though with only a moderate intake of protein. In a daily 2,000-calorie diet, that might look like 165 grams of fat, 40 grams of carbs, and 75 grams of protein.
You are also less likely to be hungry because food intake will mostly be in the form of fat and protein. Most of the weight loss will be fat and water. However in the long term it is not very sustainable. Once weight loss is achieved, ketogenic programs suggest following the diet for a few days a week or each month, interchanged with other days allowing a higher carbohydrate intake. This is to prevent the regain of the weight lost.
A ketogenic diet may be an option if other methods of weight loss have been tried but with little success. The exact ratio of fat, carbohydrate, and protein that is needed to achieve health benefits will depend on genetic makeup and body composition.
Most ketogenic plans allow foods high in saturated fat, such as fatty cuts of meat, processed meats, as well as sources of unsaturated fats, such as nuts, seeds, avocados, plant oils, and oily fish. It will be important to try to obtain the nutrients missed out from restriction of carbohydrates, through the allowed foods such as meats, fish, vegetables, fruits, nuts, and seeds.
All carbohydrate rich foods are not allowed on this diet, which can include breads, pastas, rice but also from fruits, beans and legumes. You can have certain low carbohydrates fruits, such as watermelon, peaches and berries in small portions. Vegetables, also rich in carbs are restricted to leafy greens, such as kale, spinach, cauliflower, broccoli, Brussels sprouts, asparagus, bell peppers, onions, garlic, mushrooms, cucumber, celery, and summer squashes.
There can be short term side effects such as constipation, headache, bad breath, dehydration, dizziness and fatigue.
The diet doesn’t discriminate between lean versus high in saturated fats and proteins. According to Harvard University, the keto diet is associated with an increase in "bad" LDL cholesterol, which is also linked to heart disease. It would be important to try to focus on fat and protein intakes that are lean and lower in saturated fats.
Followers of this diet also miss out on carbohydrates, a major nutrient and source of energy for the body and brain. Many foods that contain carbohydrates are foods that are also important sources of vitamins and minerals such as fruits, bread and starchy vegetables like peas and potatoes. A ketogenic diet would severely restrict these and could lead to nutrient deficiencies. Because of the limiting nature of the diet, it can be very hard to stick to in the long term.
Research on the diet for weight loss is limited. Studies have shown short term benefits only of the diet for weight loss and other health indicators. However it is not known what the benefits or effects are after one year.
It is recommended that a ketogenic diet is followed with the guidance of a doctor or accredited practising dietitian to ensure it is done so safely and in a way that meets your nutritional and individual health needs.
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