Ketosis is what happens when your body switches to burning fat instead of sugar for energy, and it only happens when you eat almost no carbohydrates (no more than 40g per day), or when you use certain kinds of oils.
Ketosis works great for weight loss in the short term, but that’s not why it’s so amazing. When you look at keeping your weight off forever, ketosis provides a level of appetite suppression that helps you literally stop thinking about food all the time.
This post walks you through one of the most important mechanisms that makes ketosis so effective for people who have tried everything else to lose weight and failed to keep it off: appetite suppression.
The Science Behind Using Ketosis to Stop Being Hungry
Ketosis suppresses appetite in more than one way. When you start eating more fat and cut out all those senseless carbs (sugar, bread, grains, and the like), you tend to stop experiencing the blood sugar swings that plague most people on the Standard American Diet. These fluctuations cause intense hunger that keeps you lurching from one carb-heavy meal to the next, never feeling satisfied—and never reaching the deep fat-burning state of ketosis. But that’s not big news to most of us.
What’s exciting is that ketones suppress appetite in a variety of more subtle and significant ways because ketones can control hunger and satiety hormones. Scientists have identified that ketones impact cholecystokinin (CCK), a hormone which makes you feel full, and ghrelin, the “hunger hormone.”
Ketones and CCK
Your intestines release CCK after you eat, and it is a powerful regulator of food intake—so much so that injecting people with CCK will cause them to cut their meals short.
Your body secretes less CCK after you lose weight. In other words, when you are thinner, you will feel less satiated with the same meal than you did before losing the weight. So you’ll crave more unhealthy foods. However, weight loss with ketosis keeps you from getting caught in this trap.
In fact, a recent study in the American Journal of Clinical Nutrition showed that even after 8 weeks of weight loss that resulted in significant reductions in CCK, just one week of ketosis returned CCK to baseline (pre-weight loss) levels. In other words, even if you use famine-level calorie restriction to lose weight, you’d better pound the butter and cut carbs at the end unless you want to crave food all the time.
Ketosis and Ghrelin
Ghrelin is called “the hunger hormone” because it increases appetite. It’s released from your stomach and intestines, with blood levels reaching their highest point during normal fasting. When you eat a meal, ghrelin drops in response to nutrients circulating in your blood.
Ketosis completely suppresses the increase in ghrelin levels that occurs with weight loss. In fact, if study subjects had ketone levels higher than 0.3 mM during dieting, their ghrelin levels actually went down compared to baseline (pre-weight loss) levels. That means they wanted to eat less after they stopped dieting, instead of more!
Because increased appetite following weight loss is one of the key factors in weight regain, this is nothing short of amazing.
How Much Ketosis Is Enough Ketosis?
So what level of ketosis does the trick? A recent study published in January 2015 in Obesity Reviews found that a blood ketone level of 0.5 mM was sufficient to significantly suppress appetite in participants on a variety of diets. Typically, circulating levels of ketones are at ~0.1 mM in the average person after an overnight fast. However, to see optimal weight loss results and hormone changes it is best to achieve 1.5-3.5 mM or higher. (just be careful not to get into the double digits as this can become dangerous.
So there you have it – there are great reasons to be in ketosis at least some of the time every week, even if it’s the kind of mild ketosis you can bring on by hacking your morning coffee.