First, a little chemistry. The ketogenic diet is not just about limiting carbohydrates, it’s more accurately described as having very low carbohydrates and high fat.
The goal is to have your body spend most of its time in ketosis (i.e., burning fats instead of carbs).
The ketogenic diet has been a staple of my health regimen because it helps me burn fat more quickly, even when I’m sleeping. I used to do intermittent fasting, where I’d go without food from dinner the night before until lunch the next day.
That changed when I discovered the ketogenic diet. Now, I only skip breakfast if I’m on an airplane or spending a long day traveling (it’s just too hard to sit through all the airport food offerings).
When you’re in ketosis, your body can efficiently burn fat for energy. On top of that, your blood sugar is more stable, muscle mass isn’t lost, and you’re less hungry.
There are also other amazing benefits to being in ketosis that aren’t as well-known:
- Your brain will run better on very low carbohydrates as there’s no glucose spillover from the blood.
- You’ll be able to use ketones for energy, making your brain work more efficiently as there’s no energy competition with the muscles.
- Your lungs will run better on very low carbohydrates and you’ll have more energy to exercise. One of the main arguments for carb-loading before a marathon is that you’ll be able to use oxygen more efficiently. If we flip this on its head and eat low carb for the week before, during and after a race, our muscles will have far less glucose available, and thus they’ll rely more heavily on fats which don’t require as much oxygen.
- You’ll have more ATP available (adenosine tri-phosphate, your body’s main energy molecule). Each link in the chain of an ATP molecule is made up of phosphorus and then a sugar, which can be glucose or ketone bodies.
When you eat carbs and your blood sugar is high, your phosphorus levels also go up.
If you eat a diet very low in carbs and blood sugars are kept stable, there’s no need for so much extra phosphorus – it’s excreted through the urine.
This causes a huge burst of phosphate in the urine that can be detected in lab tests as elevated levels.
If you consume too much phosphorus in the bloodstream, your body will pull calcium from your bones release it into your urine. The result is a bone mineralization defect called hyperphosphatemia.
What Happens During A Fast?
To really understand what happens when you come off the ketogenic diet, you have to understand what goes on during and after a fast (which is what the ketogenic diet basically is).
Your body has at least two types of fuel: glucose and ketones. When your blood sugar gets low enough, your liver starts converting fat into fatty acids and ketones.
Those ketones are used to make acetoacetic acid, which can be converted into energy in the brain and muscle tissue.
The longer you keep your glucose low enough, the more ketone bodies will accumulate in your bloodstream and urine.
Researchers have shown that athletes who work out after an overnight fast develop significantly more ketone bodies in their bloodstream than athletes who’ve eaten a carbohydrate-containing meal. All that extra fat burning, just by not eating carbs.
What about those people who fast all day, every day? They get even more ketones circulating throughout their bodies.
Studies have seen that among an assortment of diets (Atkins, high fat, Mediterranean), the highest ketone values were seen in people who followed a very low carbohydrate diet.
Going Off Being In Ketosis
What happens if you go off ketosis? Does the extra fat burning disappear, and does your body go back to burning glucose as its primary fuel source? What if you can’t stick with the keto diet?
Many people first assume that their levels of ketones their urine had gone down after a weekend eating more carbohydrate-containing foods.
A few years back, Dr. Richard Veech, a legend in the low-carb world for his seminal work on ketogenic diets and their anti-seizure effects, did a series of papers exploring what happens when you go off the diet long enough to have your glucose levels return to normal. Basically, from eating a higher carb diet for multiple days.
His research showed that it took a minimum of two weeks before there was a significant rise in blood glucose levels. In the first few hours, ketones dropped, but they bounced back to approximately 50% of their original values.
It takes about three to four days for glucose levels to get back up to normal. And if you return to a ketogenic diet, you have to wait at least six days for your blood glucose levels and ketone values to get back down to low-carb levels again.
Other doctors studied the effect of endurance exercise on people who are in ketosis. They found that even after two weeks of rising blood glucose values, ketone body concentration remained very low at all levels of exercise.
It was also concluded that the only way for these high-fat burners to get their ketone values back up would be to eat a lower carbohydrate diet (where they’d start burning ketones again) or wait for the glucose level drop to occur naturally.
If you exercise enough, jog a marathon, do Beachbody, Insanity or P90X3 three times a day for 40 minutes a session, then maybe your body would get back into ketosis quickly. But that’s not going to happen if you’re living a normal life.
Your casual weekend of not being in ketosis isn’t going to seriously impact your ability to lose fat, either.
Plus, if you go off the diet long enough for your glucose level to rise to normal levels, are you even still in ketosis? What’s considered “low” in ketosis – about 2.0 mmol/L of ketones in the blood, is equivalent to having a level of high-density lipoprotein (HDL cholesterol) over 50 mg/dL.
That’s more than most people who are not following a low carbohydrate diet have.
So, if you’re eating low carb and you’re not seeing that level of ketones, are you really in ketosis? Maybe not.
You can go off the diet and retain most if not all of your weight loss benefits so long as your blood glucose isn’t spiking higher than it was before starting the diet. Going back on a lower-carb diet will get you back to where you were before if you choose to cycle your dieting.
The take-home message is this: don’t be afraid of the carbs. When they’re not in your diet, your body burns its own fat stores for fuel. If you want to put them back into your diet, even at a smaller degree, it takes time for things to return to normal.
So, don’t be afraid of reversing any headway you’ve made, and just be mindful of your food choices if you choose to come off keto. Tracking your calories will allow you not to regain the weight you’ve lost as well.