Our nutrition experts weigh in on intermittent fasting, its benefits, use cases and potential negatives when applying it to your lean endurance protocols.
Topics Overview
What is intermittent fasting?
How does intermittent fasting make me leaner?
When should I be trying to fast?
Lifestyle and activity considerations
What are the potential drawbacks?
What is intermittent fasting?
Intermittent fasting has been very trendy in recent years.
It is claimed to cause weight loss, improve metabolic health and perhaps even extend lifespan.
Not surprisingly given the popularity, several different types/methods of intermittent fasting have been devised.
Intermittent fasting is not a diet, it's a pattern of eating. It's a way of scheduling your meals so that you get the most out of them. Intermittent fasting doesn’t change what you eat, it changes when you eat.
It is a great way to get lean without going on a crazy diet or cutting your calories down to nothing. In fact, most of the time you'll try to keep your calories the same when you start intermittent fasting. (Most people eat bigger meals during a shorter time frame.) Additionally, intermittent fasting is a good way to keep muscle mass on while getting lean.
The main reason as an active person you would attempt intermittent fasting is to lose fat. We'll talk about how intermittent fasting leads to fat loss.
Intermittent fasting is one of the simplest strategies we have for taking bad weight off while keeping good weight on because it requires very little behavior change.
How does intermittent fasting make me leaner?
To understand how intermittent fasting leads to fat loss we first need to understand the difference between the fed state and the fasted state.
Your body is in the fed state when it is digesting and absorbing food.
The fed state starts when you begin eating and lasts for three to five hours as your body digests and absorbs the food you just ate.
When you are in the fed state, it's very hard for your body to burn fat because your insulin levels are high. (Insulin tells the body to burn carbohydrates and store fat and is neccessary for glucose energy metabolism. High levels of insulin through most of the day can lead to higher body fat percentages.)
After that timespan, your body goes into what is known as the post–absorptive state, which is just a fancy way of saying that your body isn’t processing a meal.
The post–absorptive state lasts until 8 to 12 hours after your last meal, which is when you enter the fasted state.
It is much easier for you body to burn fat in the fasted state because your insulin levels are low.
When you're in the fasted state your body can burn fat that has been inaccessible during the fed state.
When should I be trying to fast?
If you are averaging less than 10 hours per week of aerobic activity you should try to consume the bulk of your calories early in the day for breakfast and lunch so that in the evening you can consume less total calories. (Why 10hrs per week? More than 10hrs and the body is needing a greater amount of round the clock carbohydrate energy and most will find they are hungry or unable to fast for long stretches)
This leaves the overnight hours of sleeping semi fasted and fasted when you are needing less energy overall. During the day we need energy to be active and work and this is not the best time to be fasting.
For most this means 6-9hrs of fasted sleep time when the body is burning fat at rest and helping you to lean out while you are in a lowered insulin state.
With less than 10hrs per week of activity you may also attempt to fast prior to your most active periods of your day. (Stick to your Lean Endurance meal plans for macro nutrient shifted foods should you need to eat.)
The Leangains model of intermittent fasting (one of many models), uses a 16–hour fast followed by an 8–hour eating period.
It doesn't matter when you start your 8–hour eating period. You can start at 8am and stop at 4pm. Or you start at 2pm and stop at 10pm. Do whatever works for you.
Lifestyle and activity considerations
Intermittent fasting does not need to be every single day but rather a strategy that is undertaken multiple times in a week. The pattern and frequency is up to you and your total activity level.
The more active and importantly intensively active you are the harder it will be to fast.
Intermittent fasting is best taken on for endurance athletes in the base phases of training before the key demands of training start to ramp up.
This type of eating is also highly encouraged in the prep and base phases of training.
Intermittent fasting will be harder to accomplish for those endurance athletes doing longer distances of training in the base phase in which the activity is great than 90minutes. For these athletes and on these days it would be ideal to skip fasting as an option and attempt it on a lighter day of activity.
All or nothing? It is possible to chose very light foods such as veggies or protein during the fasting phase when you need foods to get you over the hump. The fat burning from fasting is a “continuum” and not an all or nothing event.
You can still enter a high fat burning state by eating low glycemic foods that do not create an insulin response. (See your macro nutrient and meal plans from Lean Endurance for timing methodology)
Foods to eat during a fast
What are the potential drawbacks?
The drop out rate to such an eating schedule may be high. Meaning, it is hard to go so long without eating. (Potential Solution; it does not have to be every single day but rather a stagey used periodically.)
Lifestyle considerations; meals are social and this may not fit with your work, life and family meal schedules. (Potential Solution; Move to fasting only at night.)
Body preservation mode; When the body is under attack (Minimal food coming in) there is the potential to overeat at the next meal. To the point that it is “binge eating” or excessive. Your appetite hormones and hunger center in your brain go into overdrive when you are deprived of food. (Potential Solution; Dont fast quite as long and keep healthy options on the ready for when you have completed your fasting.
Very active endurance athletes with higher than 10hrs per week of training or more than 90minutes in a day of activity will find intermittent fasting hard to accomplish with success.
It is key to make the meals larger in order to restore glycogen for future use. For highly active individuals (Greater than 5hrs per week of aerobic endurance activity) they will need to eat larger meals to have energy to compete and complete their training.
Intermittent fasting is a great periodic strategy towards leaning out. To make sure you are not in “starvation” mode learn more below.