Get lean by adapting your body to burn fat. Being able to call on your fat stores for fuel is extremely beneficial if you want to get lean. In fact it’s critical, but hard to do. Here’s how it works:
When you eat a large portion of your diet from carbohydrates, you burn glucose for energy. One of many problems with living off carbs is that you have to continually eat them every few hours in order to maintain blood glucose levels. It’s not a very efficient way to fuel the body and it inhibits fat loss.
If you limit carbohydrates in your diet in favor of fat and protein, you can force your body to burn fat for energy rather than sugar. This dietary model is often called a “ketogenic” diet because when you burn fat for energy, your body produces ketones , which are a safe byproduct of burning fat.
Ketosis is not an “on-off” state such that you are either in it or out. It’s flexible. A mild form of it is generally ideal for the average person who wants to be lean and active. That doesn’t mean it’s for everyone. Some people seem to thrive on carbs, and there are many benefits to including carbs in the diet at certain times—but that’s an article for another day.
To better understand fat adaptation, let’s look closer at the ketogenic diet. Of interest, particularly if you are a practitioner of intermittent fasting, the ketogenic diet was first developed in the 1920s to mimic the effect of fasting in the body. Doctors realized that fasting was a way to reduce the frequency of epileptic seizures because the lack of glucose during a fast has a neuroprotective effect on the brain.
Since a person can’t fast indefinitely, doctors proposed a very high-fat, low-carb diet to have the same therapeutic effect on the brain. The high fat content led to the production of ketones, which are then used as a source of energy in the brain. The rest of the body is powered on a combination of free fatty acids, ketones, and a small amount of glucose. It’s still used today to treat epilepsy.
Despite its long history, the ketogenic diet hasn’t been accepted by mainstream nutrition because of the odd misconception that carbohydrates are the best source of energy for the body and brain. This is not correct. One scientist who ran the ketogenic diet program at Johns Hopkins wrote that “ketones are a more efficient energy source for the brain.”
The reason is that by limiting carbs in favor of the high-powered ketones, you decrease oxidative stress, minimize insulin and improve your overall metabolism. To be clear, the brain does require about a quarter of its energy from glucose, but the amount is so small that technically you don’t have to eat any carbs to fuel it. For active folks, a small carb intake is adequate.
So, what can you do to become fat adapted for optimal body composition? Should you go on a ketogenic diet?
The perfect diet for each person will be unique based on genetics, training status, and body composition. The following points can guide you in determining the ideal method for becoming more metabolically flexible:
1) Full-fledged ketogenic diets are administered by an experienced dietitian or doctor because they require strict adherence to macronutrient ratios. In the case of epileptics, the initiation of a ketogenic requires hospitalization to monitor the process.
Take Away: It’s prudent to get coaching from an experienced practitioner before radically shifting your diet.
2) Fat adaptation and mild ketosis can be achieved with a high-fat, moderate protein, low-carb diet. Optimal macronutrient intake will vary based on individual needs and body composition. One review suggests that for athletes who want to limit carbs, eating 15 to 25 percent protein, 60 to 70 percent fat, and the rest from carbs can enhance fat burning in the body. Electrolyte and sodium supplementation may be necessary.
A study of Italian national team gymnasts found that putting them on a low-carb ketogenic diet of 54.8 percent fat, 40.7 percent protein, and 4.5 percent carbs resulted in significant body fat loss without a detriment to performance. Lean mass was maintained during the trial. This study didn’t specifically test whether fat burning increased in the body, however, the gymnasts did lose 2 kg fat (2.6 percent body fat) during the 30-day study, so it’s highly likely that they improved their metabolic flexibility.
Take Away: Individual needs will dictate optimal macronutrient ratios for fat adaptation, leanness, and performance. There are various models available, and again, it’s a smart move to get an experienced coach to help you identify the best program for you.
3) Metabolic flexibility and the ability to burn body fat are extremely beneficial for health and performance. Research shows that if you are lean, it is easier for you to increase your metabolic flexibility than if you are overweight.
For example, a recent study took 12 lean and 10 obese men and had them eat a high fat diet (70 percent fat, 15 percent protein, 15 percent carb) for three days. The lean subjects increased the amount of fat their bodies burned for energy, whereas the obese subjects did not.
Take Away: One way to become more metabolically flexible if you are not overweight is to increase fat intake and decrease carbs. If you are not overweight, gene signaling and fat oxidation will quickly improve to help you run on fat if you restrict carbs. At least over the short term, obese people do not respond to such a switch.
4) Exercise can improve metabolic flexibility and help the body get into fat burning mode. In the study mentioned in #3, the same two groups of people went through a washout period, then did 10 days of aerobic exercise (1 hour a day at 70 percent of maximal). Results showed that this time both the lean and obese subjects increased fat burning in response to training. Exercise is a catalyst for the overweight to become more metabolically flexible.
Take Away: It’s critical that overweight people exercise in order to improve metabolism for eventual fat loss. Training will help shift the body to burn fat for energy. Once initial adaptations occur favoring fat burning, modifying macronutrient intake may further support the process.
5) High-intensity training with sprints or weights can further enhance fat burning in the body. Studies show that HIT training models repeatedly increase fat oxidation in lean and overweight subjects. A recent example is a 32-minute HIT strength training workout that had trained men perform 3 sets at 85 percent of the 1RM to failure with short rest periods. Results showed a significant increase in the use of fat for fuel as measured by respiratory exchange ratio.
Take Away: HIT training can further enhance metabolic flexibility and fat burning. Pairing it with diet may help you get fully fat adapted for optimal leanness.