How to Time Intermittent Fasting Around Your Workouts – Men’s Journal

By now you havent just heard about one of the latest weight-loss trends, you know at least a handful people who are devoted to intermittent fasting (IF). Maybe youve even tried it yourself.

There are a lot of opinions surrounding IF, and there are different ways to do it. So you no doubt have a few questions. How effective is it? Whats the best method? What factors into the timing? How do you fit workouts around fasting? Heres what the science actually says about it.

Jordan Mazur, M.S., R.D., is the coordinator of nutrition and team sports dietitian for the San Francisco 49ers.

Intermittent fasting has been around for centuries, since ancient hunter-gatherer times, but its risen to popularity in the past five years or so. There have been a few catalysts: a 2012 documentary called Eat Fast, Live Longer; as well as a slew of books including The Fast Diet,The 5:2 Diet Book, and The Obesity Code. All of this media, combined with anecdotal success, have created a positive buzz around the trend.

IF is an eating pattern that cycles between periods of fasting and eating. It doesnt specifically say which foods to eat or avoid, but rather when you should be eating. Its actually more of an eating pattern than an actual diet per se. Modern IF methods can be summed up by these four types:

The 16:8 method is the most popular and easiest for people to stick to. Overall, no matter what method you choose, as long as youre reducing your caloric intake, any method should cause weight loss as long as you arent over-consuming during the feeding timeframes.

Fasting causes a number of reactions in the body that affect your cells on a molecular level. The main idea behind IF is that it helps your body access and mobilize fat stores by adjusting the hormones that influence lipolysis (the breakdown of fats). Without diving too much into the science and mechanisms of how this works, here are a couple of the changes that occur in the body during periods of fasting:

Among those benefits mentioned, a recent review of the science of IF in the New England Journal of Medicine does a deep dive on current research, explaining how IF can improve metabolism, lower blood sugar, decrease inflammation, and improve chronic conditions like asthma and arthritis. Theres even evidence to show it can reduce damaged cells and enhance brain function.

If youre considering IF and like to work out or train, there are some things to consider. Theres some research that shows exercising during a fasted state can help muscle biochemistry linked to insulin sensitivity. In laymans terms: It can help regulate blood sugar levels. On the other hand, theres research to show the benefit of eating, especially carbs, before exercising.

If youve never tried it before, heres what you could experience if you fast before you train:

Our take: If youre an elite or professional athlete, dont train or compete while fasted. If youre a weekend warrior looking to improve body composition, fasted cardio might be worth experimenting with. Make sure you think through the timing of your workouts when fasting based on your goals and individual performance. Working out before the eating window while fasted is preferred for those who want to improve body composition and know they can personally perform well on an empty stomach. Working out after the eating window is ideal for those who perform better after fueling, or those who dont have the time in their schedules to work out before the window.

What you eat during your feeding window also matters. Although the concept of IF is more of an eating pattern than a diet, the food and macros you eat during the window should reflect your goals as well. If youre strength training, higher carbs and protein are needed. If youre endurance training, carbs and protein are also importantbut in a different ratio (more carbs to protein). If your goal is to improve body composition and lower body fat, then following a low-carb diet in your eating window might be ideal for you.

No matter what type of IF you decide to try, make sure to listen to your body. If you feel weak or dizzy, you might need to switch it up. Your blood sugar may be too low, or you may be dehydrated. Make sure you eat well-balanced, high-quality foods during your feeding window, and always remember to stay hydrated and include electrolytes to achieve optimal performance.

The bottom line is there are many different types of IF. Theres positive research to back it up and improve overall health. However, there are a few considerations you need to consider to pick the ideal type and timing of IF that works for you and your goals.

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How to Time Intermittent Fasting Around Your Workouts - Men's Journal