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Most people in the developed world spread their food intake out over the whole day – breakfast, lunch, dinner, and maybe a snack or two in between. But humans evolved and thrived on an irregular meal schedule well before grocery stores and modern food preservation made “three squares a day” possible. And far from being unhealthy, skipping an occasional meal or two has several benefits for health and weight loss. Essentially, fasting is a beneficial stressor, and when your body responds to the stress, it becomes stronger and healthier.
Intermittent fasting, or IF, means incorporating regular periods of fasting into your meal schedule. Some people fast for 24 hours once or twice a week, while others incorporate shorter but more frequent fasts by restricting their daily caloric intake to a window of 4-8 hours. Fasting is most commonly understood to involve no food consumption at all, but Paul Jaminet at the Perfect Health Diet also argues for the consumption of coconut oil or bone broth during a fast.
Intermittent fasting is a logical extension of the Paleo diet, for people who want to eat not only what they evolved to digest, but when they evolved to digest it. Eating Paleo also makes fasting relatively easy: if you avoid refined carbohydrates, your energy levels don’t spike and crash with every meal, so you shouldn’t experience wooziness or “brain fog” during a fast.
Conventional diet wisdom discourages skipping meals, which is often associated with eating disorders and unsustainable crash diets. Deliberately practiced intermittent fasting, however, can be a powerful tool for weight loss.
Most obviously, fasting involves caloric restriction – and many people find it easier to fast than to count calories. When you fast, you quickly stop feeling hungry and can turn your attention to other things, and then conclude the fast with a satisfying meal. Counting calories, on the other hand, makes it easy to fixate on restricting food intake, leading to persistent feelings of hunger and deprivation as you eat several unsatisfying meals throughout the day.
Hormonal changes involved in fasting also promote weight loss, even if you don’t restrict calories. Fasting lowers the body’s levels of insulin, a hormone that prevents the release of stored body fat. With lower insulin levels, your body turns to stored fat for energy. Additionally, fasting increases other hormones called catecholamines, which trigger your body to use energy at a faster rate. This makes fasting a particularly useful tool for dieters, since it promotes the loss of fat rather than muscle mass.
At first glance, athletic training in a fasted state seems contradictory: how can your body perform without fuel? But intermittent fasting can actually improve athletic performance, as long as you don’t fast for too long.
For endurance athletes, the benefits of fasting come from a two-pronged approach: training in the fasted state, and competing in the fed state. Fasted training can improve performance by forcing your body to adapt to lower glycogen stores and use glycogen more efficiently. Essentially, training in the fasted state adds another stressor, forcing your body to compensate and become stronger. This sets you up to get a huge boost from competing in the fed state – your body will make maximum use of your pre-workout fuel.
Short-term fasting is also useful for power athletes. While fasting for several days at a time will hurt your progress, intermittent fasts less than 24 hours will not cause muscle loss or send your body into “starvation mode,” as long as you consume adequate calories and protein when you do eat. On the contrary, when you lift in a fasted state, your body uses protein more efficiently afterwards, boosting muscle growth. Weightlifters seeking to gain lean mass without also gaining fat should look into Martin Berkhan’s Leangains program, which specifies an eight-hour “feeding window” and a sixteen-hour fast every day.
As well as weight loss and increased athletic performance, your body’s response to the beneficial stress of fasting can help promote health and longevity in a variety of other ways.
First, fasting can help cancer patients. Although the relevant research was conducted on animals, one study showed that rats who fasted every other day showed greater ability to fight off chronic diseases like diabetes and cancer, and improved heart health. Fasting helps fight these diseases because when you stress your cells by fasting, they enter “survival mode,” giving them increased resistance to stress, while cancer cells remain in “normal mode:” this gives your cells the advantage. In study on humans, scientists found that fasting can also reduce the risk of heart disease.
Fasting also promotes health by reducing oxidative stress. Oxidative stress, or damage to your cells from a harmful build-up of oxidized proteins, is linked to the harmful effects of aging. Fasting helps your cells get rid of these oxidized proteins. A study done on humans with asthma showed a reduction in oxidative stress and improved heart health on an alternate-day fasting regimen even when the “fasting days” actually involved very low food intake.
As well as benefitting your body, fasting is also good for your brain. In the same way that it helps your other cells, it increases brain cells’ ability to repair themselves and eliminate potentially harmful waste material. It also triggers the body to release more of a protein called brain-derived neurotrophic factor (BDNF), which supports healthy brain function and prevents degenerative disorders like Alzheimer’s disease.
On top of its other health benefits, intermittent fasting also helps some people who suffer from troublesome circadian rhythms, since circadian rhythms are even more strongly tied to eating patterns than to light exposure. Even if your circadian rhythms are normally fine, fasting can help beat jet lag by “resetting” your internal clock to the new time zone.
While most healthy adults following a Paleo diet should have no trouble with intermittent fasting, it’s not for everyone. Before adding IF to your routine, make sure your body has fully adjusted to eating Paleo. Fasting is a stressor to your body, so it can do more harm than good if you’re already under any kind of chronic stress. If you’re sleep-deprived, suffering the effects of overtraining or chronic lifestyle stress, leptin resistant, or if you have blood sugar problems, IF is not for you. You should not feel sick, dizzy, or inexplicably exhausted during a fast: if you do, eat something. Think of IF as the cherry on top of your Paleo chocolate pudding: first work on the fundamentals (adjusting to the dietary changes, getting enough sleep, and reducing chronic stressors), and then consider adding it to your routine.
If your body is able to handle the additional stress, intermittent fasting can lead to faster weight loss, improved athletic performance, and a long list of other health improvements. Easy to practice and safe for most people, IF can be a great addition to a Paleo diet.
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