What is a low carb diet?
A low carbohydrate diet is one in which carbohydrates are limited to less than 120 - 130g per day and more high fat foods are consumed. Low carbohydrate diets like the ketogenic diet (where less than 50g carbohydrates are consumed per day) have become more popular in the last 5-10 years but have been used to treat certain medical conditions for centuries. The keto diet is often used to help manage Type 2 Diabetes and is an effective treatment for children with epilepsy where medication is ineffective. More recently, it has gained much popularity as a weight-loss strategy.
How do low carbohydrate diets work?
In essence, low carbohydrate diets aim to change the kind of fuel that the body uses for energy.
The main source of energy for all the cells in the body is glucose (sugar), derived from carbohydrate containing food such as grains, legumes, vegetables and fruit.
On low carb diets, the cells rely on ketone bodies for energy. This is the fuel that is produced from broken down fats in the liver in a process known as ketosis.
One can reach ketosis (“burning fat”) and get the liver to produce ketone bodies in about 2-4 days if consuming less than 50g of carbohydrate per day (a medium banana has about 27g). After about 4 days of a very low carbohydrate intake and once all the glucose stores have been used, the body will start to break down fat for energy. This process can take a bit longer depending on various factors such as age, activity level and amount of carbohydrate, protein and fat intake.
Ketone bodies can replace glucose as an energy source even for the brain.
How does it lead to weight loss and the research so far?
There are several mechanisms in which weight loss can occur when following a low carbohydrate diet, here are 3:
Following a low carb diet has been linked to decreased levels of the body’s hunger hormone, Ghrelin. This causes less calories to be eaten in the day, leading to weight loss. In a systematic review of 26 short-term intervention trials, appetite was evaluated in individuals who where overweight or obese and followed a ketogenic diet (low carbohydrate diet) or a very low energy diet. Participants reported being less hungry and having less desire to eat at the end of the diet compared to before the diet began. The authors theorised that this was due to the changes in hunger hormones, increase in ketone bodies and increased consumption of fat and protein.
Loss of water weight
Carbohydrates that are stored in the body hold water. When you reduce your carbohydrate intake, carbohydrates are released along with water leading to a loss of water weight.
There is a reduced calorie intake as a result of changes in the satiety (fullness) signals that are associated with low carbohydrate, high fat diets. There is also increased energy expenditure because of the metabolic effects of converting fat and protein to glucose. The body expends more energy when it needs to convert fat and protein to glucose. The evidence provided by a review of published meta-analyses and systematic review of trials of diets for diabetes remission, found that there is uncertainty about the effects of low carbohydrate diets on weight management and type 2 diabetes remission. While very low energy diets and formula meal replacement were found to be the most effective approaches for weight loss in people with type 2 diabetes, one non randomised control trial reported a 20% remission rate.
What is included on a low carbohydrate diet?
When following a low carb diet, fat is usually included at every meal. Unsaturated, healthy fats like avocado, nuts, seeds, olive oil and tofu are incorporated as well as saturated fats such as coconut oil, butter and cocoa butter.
Protein is encouraged at about 75g per day for someone on a 2000 calorie per day meal plan and sources of lean protein as well as those high in saturated fat like pork, bacon and beef are encouraged.
Certain fruits and vegetables are included such as berries in small portions, all the green leafy vegetables as well as other low carbohydrate vegetables like mushrooms, bell peppers, cauliflower, broccoli, brussels sprouts, cucumber, onion and celery.
Remember to consult with your dietitian when following a low carb diet so that the meal plan can be tailored to your specific needs and your progress can be carefully monitored. Feel free to contact our team of experts for hands-on assistance and advice in this regard.