Intermittent fasting is another fitness industry trend that is probably not going away anytime soon. This goes completely against the face of all conventional health advice, including those that tell you to eat a balanced diet three times a day.
As its name implies, intermittent fasting means you have to go without food for a certain length of time and only eat within a prescribed feeding window. There are two common intermittent fasting schedules that seem to work well for most people.
The first and more extreme schedule is Eat-Stop-Eat, a method popularized by author Brad Pilon. If you choose to go by this method, you have to skip meals for a 24-hour period, before resuming your regular eating pattern for the next 24 hours. Typically, fasting is done from dinner of the first day to dinner of the second day.
The second schedule is far less severe and is more suitable for beginners. This involves skipping breakfast (gasp!) and eating during an eight-hour feeding window that begins from 12 noon to 6 p.m.
Some schools of thought believe you have to eat only certain types of food – mostly protein and fat – while fasting intermittently. Others say you can eat a good balance of all three macronutrients and an abundance of fruits and green vegetables for fiber.
There is no consensus among pundits, as the scientific community is only beginning to try to make sense of intermittent fasting. But early studies are very promising, at least for men. As this study shows, fasting for not longer than 48 hours actually boosts your metabolism, but going longer than that might not have the same effect.
One explanation for the metabolic boost that happens might be the hormonal changes that take place when you skip meals. When your body realizes that you’re not eating anything, your insulin drops, followed by an increased ability to use stored fat transformed into ketone bodies for energy. In men, intermittent fasting also appears to increase insulin sensitivity, but the same effect has not yet been tested in women.
This is compounded by a nervous system reaction that releases the hormone norepinephrine, which heads straight to the fat cells and breaks them down to release more fatty acids to be burned for energy.
Furthermore, human growth hormone (HGH), considered a gem in fitness circles for its ability help with muscle growth and fat loss, goes through the ceiling by as much as five times more than the usual amounts.
You might think this is all theory, but these actually translate into practical, tangible results. Because intermittent fasting allows you to eat naturally fewer calories, it can help you lose weight by 3% in three weeks and 8% in 24 weeks. For alternate-day fasters, that amounts to 1.65 pounds lost every week.
The effect is not as profound in people using the 16-8 method, but they still lost 0.55 pounds every week and 4% to 7% of waist circumference just by changing their eating schedule.
1. Do high-intensity interval training.
Most people think logging in hours at the treadmill is the way to go. But while steady-state endurance exercise can help generate more of the muscle hormone irisin, and irisin can help increase brown fat, which encourages fat loss, it’s not really the best kind of cardio.
Doing loads and loads of cardio may help you lose weight, but that’s at the expense of losing muscle as well. The better alternative is to do high-intensity interval training (HIIT) instead.
You may have heard fitness coaches and amateur gym buffs touting HIIT. It’s a faster, although not necessarily easier, way to lose fat by doing cardio.
HIIT works like this. You exercise for a short time period of very high intensity, followed by another period of low intensity, which serves as your rest. You can pretty much do any exercise on HIIT.
If you like running, for example, you can sprint up an incline for 10 seconds, followed by 30 seconds of slow jogging to rest. The principle works the same if you’re more into cycling, swimming, rowing, or whatever.
So why HIIT instead of endurance training? Two things. First, research shows HIIT can burn up to two times more fat than steady-state cardio. And second, you get more from a half-hour’s worth of HIIT than an hour or even two hours of steady-state cardio.
One study shows that people who did HIIT for 15 weeks saw up to nine times more fat loss than people who went through a steady-state cardio programs at low and medium intensity for 20 weeks. That’s a massive difference between the effects of the two exercise programs.
Another study shows women doing HIIT can easily switch from cardio-burning to fat-burning mode after only seven sessions spread out over a period of two weeks.
Another study shows HIIT can induce the body to switch into fat-burning mode after only seven sessions spread out after two weeks.
The reason HIIT works so well is that it increases mitochondrial density in the cells. Steady-cardio does this too, but you have to exercise for at least an hour before effects on the mitochondria take place.
Okay, gear up for a little bit of high school biology. As you may or may not remember, mitochondria are called the powerhouse of the cell for one and one reason only. They produce the energy our body needs to live and thrive.
When you have more and bigger mitochondria, your cells can produce more energy that your muscles can use for longer periods of time. In other words, more mitochondria leads to more energy leads to more intense exercise leads to faster fat loss.
And HIIT comes into all of this because it can help you generate the same amount of mitochondria if you do three short HIIT sessions per week as you would if you did five one-hour sessions of long, boring cardio a week.