Every animal on planet Earth has evolved to withstand long periods of time without eating, but the modern civilized human eats three square meals per day and rarely experiences hunger. Science has uncovered highly beneficial biological effects of fasting, but nobody seems to care. In this article, I hope to debunk all the ridiculous fasting myths and show you all the benefits of fasting.
First, let's agree on what a fast is. It's very simple. A fast is a period of time when you're not consuming calories. You can drink water. You can consume things like sparkling water, black coffee, maybe some sugar-free gum, and other things with negligible calorie content. You fast every night when you go to sleep, although this fast usually isn't very long because of breakfast. So let's talk about that.
You've probably heard that breakfast is the most important meal of the day. A quick Google search will reveal articles from honest-looking websites (such as WebMD) that claim to describe why breakfast is so important. They use vague claims like "breakfast kick-starts metabolism" and they go on to over-simplify blood glucose's role in metabolism. Or worse, they warn that if you don't eat breakfast you'll probably snack on junk food - as if fasting takes the blame for legal crack-cocaine. I don't buy it and neither should you.
So let's talk about human metabolism a bit. Specifically blood glucose. Glucose is the preferred fuel of your body if available. When you eat bread, fruit, beans, or anything else with carbohydrates, your body enters a "fed" or "growth" state triggered by hormones like insulin. Insulin regulates blood glucose levels by causing glucose to be absorbed by your liver, fat, and muscles. If blood glucose levels get low, three things happen: insulin levels drop, hunger hormone ghrelin is released, and your body taps into the glycogen energy reserves in the liver. Then, once your liver runs out of glycogen you'll get another dose of ghrelin while your body's metabolism switches to a completely different mode of operation: the fasting state, also known as ketosis.
And for some reason, everyone is afraid of ketosis. So let's set the record straight. When you're fasting, your body breaks down stored fat to produce ketones, which are then used for energy instead of glucose. Ketones aren't as efficient as glucose, so your body produces more than what you need. The excess is excreted in your urine. This could be bad for someone who has a dangerously low BMI, but this isn't a big concern in developed countries like the US of A where 70% of the population is overweight. Fasting is a perfectly natural way to lose weight - you literally urinate the fat out of your body.
So, what are the side-effects? Well, you'll get hungry. This will be fairly intense at first because you have a low tolerance to ghrelin. As you fast more frequently, the feeling of hunger won't affect you as much. So this isn't a big deal. You should get over it, in the same way you "get over" being winded from doing a few jumping jacks if you want to get healthier. Your body may get tired, and you may experience light-headedness or mental slowness. This is because your body is adjusting and it doesn't know how much ketone to produce. Again, get over it. As you fast more frequently, your body will learn to increase ketone production so you won't feel lethargic anymore. You may also get intense feelings of energy in your body - again this is a temporary adjustment that mellows out over time. You'll feel a desire to eat, not just because you're hungry but because you're craving the endorphins of the eating experience. You're addicted to food and you'll get over it with enough practice. That's it. A healthy person can fast up to 30 days without hurting themselves.
So then what's the benefit? Fat loss is the number one benefit obviously. In the fasted state, 90% of weight loss is pure fat, while only 10% is lean mass. And the lean mass lost to fasting is primarily in the digestive system, not from muscle tissue. This is the main detail that many medical resources (ahem, WebMD) get totally wrong. Losing weight to a low-calorie diet is 80%-20% fat to lean mass lost, where a higher percent of lean mass loss comes from muscle tissue. This is a no-brainer. Fasting is definitely the better choice for losing fat.
So then why do so many resources recommend a low-calorie diet and condemn fasting? The food industry is to blame here. They've been spreading propaganda about nutrition for decades. Look at the bottom level of the food pyramid for example. It's all processed grains. You don't need to be an expert to realize that humans did not evolve to primarily eat grains. Grains have been an important aspect of the human diet for practicality and cost reasons - not because of nutrition. Dairy also does not belong here - humans have only recently developed a mutation which allows us to consume dairy beyond childhood. That's right - about ten thousand years ago every human on Earth was lactose intolerant. Back then we got all the calcium we needed from leafy greens, and all the Vitamin D from the sun. You don't need grains or milk to survive - this is nonsense.
The food pyramid isn't about what we should eat - it's about what the food industry wants us to eat. Take a look at your local supermarket for example. Look how much space is devoted to grains: bread, crackers, breakfast cereals, and baked goods. These products are lucrative because they taste good, they are cheap, and some brands boast high profit margins. But they also represent the worst processed food mankind can offer - often artificially fortified with some vitamins and minerals to give a healthy impression.
We're told that low calorie is the best way to diet - this is also a lie intended to increase your consumption of carbohydrates. Why? Because carbs have a lower calorie density than fats or protein. So if you're on a low-calorie diet and need to choose between a chicken breast (140g, 230 Cal) and a cup of cooked rice (158g, 206 Cal) then you would probably choose the more filling, lower calorie option. Even a Snickers bar has 215 Cal, and a liter of Mountain Dew is only 110 Cal. So you can see that a low-calorie mindset alone will lead you to some very bad habits indeed.
But wait, there's more! There are tons of benefits to fasting. It can prevent the onset of diabetes, in fact Dr. Jason "Diet Doctor" Fung, MD is known to reverse type 2 diabetes in his patients with fasting. Extended fasts have even more benefits, including autophagy, increased HGH production, and more. Fasting doesn't cost anything, it doesn't require complicated preparation or meal planning, it's safe, it's effective, and it's healthy.
So please, stop spreading misinformation about fasting. Maybe even give it a try sometime.