If you’ve been paying attention to diet trends, you’ve probably noticed the latest obsession with intermittent fasting. This isn’t so much a straight diet as it is an eating pattern: You limit how many calories you eat during specific days or hours, so you cycle between fasting and non-fasting periods. With claims that benefits range from weight loss to a longer life, more and more people are trying it. We talked to Dr. Luiza Petre, a cardiologist and weight management specialist, to find out more.
What Is Intermittent Fasting?
Intermittent fasting has you feast and abstain on a specific schedule. Certain studies have shown that long-term caloric restriction has led to extended lifespan in monkeys. And a 2003 study published by the National Academy of Sciences showed that rats who fasted intermittently were healthier compared to those who were on a continuous restricted caloric diet — they had lower glucose and insulin levels and a higher resistance of neurons in the brain to stress. While the benefits to humans are still yet to be completely proven, fasting itself is not a new phenomenon — people have been doing it for centuries for various reasons, including religious ones.
When you fast, your body starts to burn fat for energy instead of burning glucose. Fasting also makes your body more sensitive to insulin, which is a good thing, so you end up with more stable blood sugar levels. This combination helps you lose weight over time. But fasting for long periods of time is not easy or practical in most cases, and that’s why intermittent fasting has become an attractive alternative — days of eating very little are balanced with days of eating normally, you don’t constantly feel hungry and deprived, and you’re more likely to stay on it.
There are several methods you can follow, but the most popular one uses a 16:8 ratio, which means you fast for 16 hours, then eat during an eight-hour window during the day. Another common intermittent fasting ratio is the 5:2. It restricts you to 500-600 calories for two days per week but allows you to eat normally during the other five days.
“My favorite and easiest time ratio to implement is the 16:8,” Dr. Petre shares. “Out of the 16 hours, you only have to fast for approximately eight hours, because you’re asleep for the other eight. It’s sustainable and easy to maintain. Also, I find it more physiologically sound, as our body has its own clock (called the circadian rhythm), and our hormone levels process food easier during the day.”
And the good news is that most people don’t experience significant side effects. Dr. Petre points out that you may have to deal with cravings, low energy, and hunger at first. But as your body gets used to intermittent fasting, these problems tend to disappear.
What Can You Eat?
Neither the 16:8 nor the 5:2 intermittent fasting diet tell you to avoid specific foods. Instead, they focus on limiting calories during certain hours or days of the week. Of course, this isn’t an open invitation to indulge in junk food during your feasting hours. Dr. Petre recommends choosing nutrient-dense, unprocessed, fresh, and whole foods. “Most of all, I recommend making protein a priority,” she adds. “Protein keeps you satiated, increases mental clarity, stabilizes blood sugar, boosts energy, and supports your bones and muscles, all while helping maintain your weight. This should be your main source of calories.”
Dr. Petre also encourages dieters to eat organic greens and vegetables like kale, spinach, and onions. She recommends eating them raw, steamed, or baked with seasonings. And you don’t want to forget about healthy fats. However, you should eat carbohydrates sparingly because they’re calorie-dense and can cause cravings. Dr. Petre tries to avoid pasta, bread, cereal, rice, potatoes, and fruit juices.
Does It Work?
If you’re looking for a different diet plan that can fit around your schedule, you may want to try intermittent fasting. Dr. Petre admits she was her own guinea pig, trying the intermittent fasting diet on herself first. After she loved the results, she started to recommend it to her patients. “We have many patients who have lost 40 pounds and more in a four- to five-month time frame.” But intermittent fasting isn’t a quick-fix diet; it’s a life-long commitment. Dr. Petre recommends thinking of it as a permanent lifestyle change, and you can do it as long as you like.
This eating strategy tends to work because, according to Dr. Petre, “First, there’s no regret, guilt, or real deprivation on this diet. People rebound and feel frustrated when restricted all the time, but with intermittent fasting, that isn’t an issue. It’s also flexible enough that it could be overlapped with another diet such as ketogenic, vegetarian, Mediterranean, or DASH. Finally, it’s sustainable! People can stick with it.”
As always, check with a doctor if you have questions beginning a new diet.
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