The human can run on two fuel sources. One is glucose and the other is ketones. If you keep glucose in short supply the body will use ketones to keep it alive and healthy. For those that would love to see a very informative video about ketosis you can click here.
The liver is the organ that produces ketones from fat. This energy source is used throughout the body, especially the brain. The brain is a very hungry organ and consumes vast amounts of energy. It can't run on fat directly but can run on glucose or ketones.
This has been demonstrated in several meta-analyses of all top studies, for example this one:
Dr Eenfeldt originally worked as a family physician. In 2007 he started a Swedish website called kostdoktorn.se that became the country’s largest health blog. In 2011 he started an English version, DietDoctor.com, and in 2015 stopped working as a physician to devote himself to the site full time. The website is the largest low-carb website in the world and employs 14 staff with 200, 000 visits a day
Although the brain is roughly 2% of body mass it burns about 20% of the body’s energy every day,
This is a good bonus for weight loss, if you can get your hungry brain to burn fat for you, 24-7.
Another note: ketosis is why the old idea that “the brain needs carbohydrates” is wrong – the brain requires limited amounts of glucose even in ketosis, but the body can create that glucose from protein and fat in a process called gluconeogenesis.
When eating the Ketogenic way the body burns fat 24/7. This is because when insulin is very low the body dramatically increases its fat burning. Put simply it becomes easier to access your fats store to burn them off. See a study here
For most people it appears to be very safe but there are some groups that need more preparation and guidance.
The most important element is to avoid carbohydrates as much as possible. The most stated figure is 20 grams a day or less. The fewer the carbs consumed the more effective this way of eating appears to be.
A high level of healthy fats is recommended on the ketogenic way of eating.
Basically this will be around 75% of the energy you consume.
Only about 15-25% of your energy consumed should be from protein. More than this and you'll find that the body may convert 'excess' protein into blood sugar.
Remember fat stores more calories per gram than carbs or protein so 70% fat in your diet is NOT 70% of your plate!
When you look at a ketogenic diet plan where fat is between 70-75%, it doesn’t mean 70% of the volume of the food, but it is the 70% of the total calories.
Above ground vegetables are generally lower carb and green leafy veg is particularly good for your health. The carbohydrates in vegetables comes in the form of fibre, this has a minimal effect on blood insulin.
If you are on warfarin, used to treat or prevent blood clots, then this can be affected by changes in your vegetable intake.
Check out this great video that explains why simply counting calories is not the best way to lose weight.