You’ve probably heard of intermittent fasting. Celebrities like Jennifer Lopez and Beyoncé have talked about it on Instagram. Hugh Jackman used it to get shredded to play Wolverine. It’s a whole different approach to dieting.
There are so many different diets today — paleo, keto, Mediterranean, raw vegan — but they all focus on what to eat. Intermittent fasting is different because it focuses on when to eat. That’s also why intermittent fasting, or IF, is also called a time-restricted diet, with one form called an “eight-hour diet.”
The basic idea behind IF is that you put your body into a fasted state by not eating or drinking any calories for an extended period of time, and then only eat during a limited window of hours. For example, since there are 24 hours in the day, if you fast for 16 hours, you have eight hours to eat and drink your calories. There are other fasting variations, too.
How a fasted state helps lose fat
Although research isn’t conclusive about some of the purported benefits of IF, and many nutritionists remain skeptical, Gold’s Gym Wellness Director Connie Cheng says that “the research is significant enough that people can use this as a method to lose weight safely.” She adds that beyond the scientific studies, there’s too much anecdotal evidence to ignore.
The problem with frequent meals throughout the day is that you’re never tapping into a fasted state. The food is giving you glucose, which is a form of energy for your body. It’s easily available after you eat, so you’re burning glucose instead of fat.
It takes about 12 hours of not having calories to get into a fasted state where you’re tapping into fat stores for energy.
Some studies have found that, for certain people, the fasted state can be useful for managing your blood sugar. Eating several times a day means your blood sugar is going up several times a day, which can lead to crashes and that hangry, up-and-down feeling.
Some studies show that a fasted state is a great way to preserve lean muscle mass while losing fat. “If done correctly and done well, 90 percent of the loss is fat and only 10 percent is muscle,” says Cheng.
When you fast for longer periods of time, your body goes through autophagy, a stage during which it recycles damaged cells and releases triglycerides, a type of fat found in the blood, to use as energy (since it isn’t getting any from food).
And there’s good news about IF for gym goers, Cheng says. “Research shows it does not impair your ability to exercise.”
How to do intermittent fasting
“Give your body time to be in a fasted state,” Cheng says. “There are several ways of doing it, and there’s no such thing as a ‘right way,’ just what works for you.”
Cheng recommends her clients begin with a 12-hour fast. Most people time their fasts to coincide with their sleeping hours.
It can be barely noticeable, she says, if you stop eating at 9 p.m. and don’t eat until 9 a.m. the next day. From there, she recommends adding an hour a day to your fasting time to get your body used to going without calories.
Look at different IF options and consider your schedule and social pressures. Many people have found IF successful because it shortens the amount of time they have to think about making or getting food.
During your fasting state, you are free to drink water, black coffee and plain tea. Consuming calories — including cream and sweeteners — will break your fast. You can use water to curb feelings of hunger.
Intermittent fasting plans
Different plans can teach you different things about your own eating habits. “You start to feel what true hunger feels like, instead of boredom,” Cheng says. “So [intermittent fasting] increases your awareness of what feeling full and hungry is like. Behaviorally, it really helps those people who are emotional eating.” (Our hunger scale can also help you determine if you’re hungry or just bored.)
For some people, IF works because in that eight-hour eating window you can fit two or three meals, but it’s such a short window of eating that you feel fuller.
“It’s actually really simple,” Cheng says. “People feel intimidated because they think, You’re starving! But actually you’re spending a lot of your fasting window sleeping, especially on weekends.”
16:8 intermittent fasting
Take at least 16 hours to keep your body in a fasted state and eight hours to eat. You can do this every day — it’s the equivalent of cutting out breakfast and late-night snacks. Some research recommends eating breakfast and lunch and skipping dinner, but it’s all about shaping the fast to your schedule. This allows your body to consume fat calories during your fasted state every day.
5:2 intermittent fasting
In this plan, you can eat regularly for five days of the week, and fast for two days of the week. During your fasting days, you’d want to consume no more than 600 calories each day. The two fasting days should be nonconsecutive, and they will be the days your body goes into a fasted state to consume calories from fat.
Alternate day intermittent fasting
Every other day, you put your body into a fasted state by consuming less than 600 calories. Alternate fasting days with regular eating days. Your body consumes fat calories every other day in a fasted state.
Risks and warnings
Intermittent fasting isn’t for everybody, and adjustments will probably be necessary based on your lifestyle. “You want to think [about] how it can fit in your social and personal life,” Cheng says. Always consult with your doctor before changing your diet.
Social butterflies and family people
For people with a very active social life, IF can be a real drag. If you’re having a romantic dinner, it doesn’t allow for that late-night bottle of wine. If you have kids, your eating window might not fit within their eating window.
People with eating disorders
A psychological hazard of fasting is that sometimes breaking a fast can lead to binge eating. “Some people take those feeding times as binge times,” Cheng says. If that’s something you need to work through, then this might not be the perfect method for you. If you’ve had anorexia or bulimia, fasting can trigger those disorders.
Diabetics and hypoglycemics
If you’ve had blood sugar issues and they’ve been poorly managed, you should get a handle on those problems first.
There haven’t been many studies on fasting’s effects on pregnant women since nutritional requirements change so much during pregnancy. Talk to your doctor to see what’s best for you and your baby.
People with digestion issues
Those shorter eating windows can mean larger volumes of food, which mean more intense digestion. People with irritable bowel syndrome or a sensitive gut can experience pain or bloating. You might want to eat at regular times to make sure you have regular bowel functions.
One of the positive stories about IF that Cheng cites is about a woman named Gwen, a client of hers (whose name has been changed).
Gwen, who had poor emotional control over her eating, was having a hard time losing weight. Because she had already tried so many different things, Cheng suggested trying IF. “I did an extensive interview on what her routine looked like and whether her social life would support it,” she says.
Gwen was single and living by herself, so she didn’t have a lot of demands holding her back. She was a perfect candidate. Cheng started her with a 12-hour fast; within a week, Gwen was at an eight-hour feeding window.
“Fasting is such an intimidating word,” Cheng says. “She was shocked by how little she had to change.”
Gwen just had to get over not eating breakfast. Then, she had to get over being a constant grazer. But since she knew she only had an eight-hour window, she had a sense of freedom of what she could eat.
“She ate less impulsively,” Cheng says. “She started shedding fat.” It took about seven weeks for Gwen to see the effects, but she was ultimately happy to have found a way to balance weight loss and healthier eating.
“Intermittent fasting is not a magic potion,” Cheng says. “It’s not a one-size-fits-all deal. It’s another tool in the toolbox.”
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