We are used to the idea that carbs provide energy for exercise, so it is understandable that people are concerned about how to incorporate exercise with a low-carb diet like the ketogenic diet.
First – let’s go over how the body gets its energy while on the ketogenic diet.
Our bodies were designed to be fat burners. Our ancestors lived off meat and vegetables. There are carbs in vegetables, but in those times our ancestors weren’t eating enough carbs, that their bodies needed to learn how to use it for fuel. They were using the meat and fat for fuel.
Fast forward to today.
Carbohydrates are consumed in abundance. This abundance of carbs forced the body to start learning how to process it and use it for fuel.
Now, when you consume carbohydrates, your body converts those into glucose and uses that glucose as fuel. It is a very quick process. This is why, when you are feeling like you need a little energy, you can have a candy bar and feel perkier almost right away.
It is also why, in the afternoon, you tend to start feeling drowsy. Your body has used up its glucose reserves and you need to replenish them.
But why doesn’t your body just keep using fat, rather?
The simple answer, is Insulin
Insulin is a hormone. It is used to help the glucose in your bloodstream travel through, allowing your body to use it as energy.
It is the insulin that prevents the fat stores in your body from being released.
So when you have the insulin being produced to help transport the glucose, at the same time the fat stores are not being released. This is why your body can’t simply flip the ‘fat burning switch’ easily.
It is only when you reduce your carbs to a very low level, so that your glucose levels drop, that your body won’t be producing the same insulin as before. This then makes it easier for the fat cells to be released.
Ok, so now you know how your body uses fuel, but how does it relate to exercising on keto?
Different Types of Exercise
Aerobic – or cardio – exercise is anything that lasts longer than 3 minutes. Low intensity, steady-state cardio is ideal for the keto dieter, as it puts you in a fat burning state. However – high-intensity cardio will require carbohydrates (we will go into a bit more detail further down).
This is characterized by shorts burst of energy. Both sprinting and weightlifting is considered anaerobic activity. Glucose is needed for this type of exercise – which we will go into a bit more detail further down.
Yoga and other stretches fall under flexibility exercises. They are good for stretching your muscles, increasing your range of motion, and supporting the joints. Being flexible also means you will tend to recover quicker from injuries.
Core training and balancing exercises help strengthen your core, improve your posture, and strengthen muscles
As you have seen above, certain types of activities – high-intensity activities, specifically – will require glucose.
Glucose can be burned during aerobic (with oxygen) and anaerobic (without oxygen) activities. Ketones can only be burned during aerobic activity.
This means that purely anaerobic activities such as a 100 yard sprint, or olympic weightlifting, actually require glucose.
On the other hand, low intensity exercises like walking, jogging, cycling (if done at a low enough intensity), don’t specifically require glucose.
When you limit carbs you are depriving your muscles of the glucose it needs to fuel high-intensity activities. This means that a ketogenic diet can actually have a negative effect on your performance if you take part in high intensity activities such as
- Sprinting or swimming
- High Intensity Interval Training (HIIT)
- Sports that have minimal rest, such as soccer and rugby
And other high-intensity sports and activities.
So, if your exercise falls under low-intensity cardio, flexibility, or stability, then you can carry on with your keto diet as normal. If you are just about to start a ketogenic diet for the first time, be aware that your performance may be affected for the first 3-4 weeks. Take it a little easier and rather focus on getting your eating right, then you can resume your activities as normal.
However, if your exercise is anaerobic, or high-intensity cardio, then you will need to talk to your coach to be put on a alternative diet plan.