Can Intermittent Fasting Help You Lose Weight?
By Elizabeth Levinson, MD — Virtua Family Physician
Americans are always looking for the best, most effective form of weight loss. That’s why the diet industry is a multi-billion dollar business. But diet crazes and fads come and go, and many of them aren’t effective in the long term. The most recent—intermittent fasting—is an eating pattern that involves regular, short-term fasts, or periods of time when you eat few or no calories.
Intermittent fasting is receiving attention from the media as it becomes popular amongst celebrities. Supporters say that it promotes weight loss or weight maintenance while helping maintain muscle mass and control insulin levels.
While intermittent fasting—also known as the “IF” or “fast” diet—is trendy, you might wonder if it actually works AND is safe.
How does intermittent fasting affect my body?
When you fast, you consume fewer calories than normal—or no calories at all—which reduces your overall calorie intake. Reducing your calorie intake can help you lose weight, but it also causes several changes to the way your body stores and burns fat.
Insulin, a hormone produced by the pancreas, converts glucose (sugar) in your blood into energy that your cells use as fuel. Insulin also drives fat storage. Your body’s insulin levels increase when you eat and decrease when you fast. Lower insulin levels resulting from fasting can prevent additional fat storage and help your body mobilize stored fat.
What are the different intermittent fasting patterns?
Intermittent fasting involves consuming all of your calories within a short period of time. There are many intermittent eating patterns, so it’s important to choose one that’s right for your body, your activity level and your lifestyle. Here are two popular options:
The 16:8 Diet
The 16:8 diet involves fasting for 16 hours each day and consuming all of your calories during an 8-hour window. Many people who follow this 16-hour fast eat 2 meals between noon and 8 pm, but you can adjust the 8-hour window to suit your lifestyle, exercise habits and work schedule. With this option, however, plan your eating so that the majority of the fast occurs during your normal sleeping hours. This will help you avoid feeling hungry during your waking hours.
The 5:2 Diet
Another popular option is the 5:2 diet, which involves 5 days of normal eating and 2 days of eating around 500-600 calories per day. The 5:2 diet gives you the flexibility to choose the 2 fasting days that work best for you, as long as they’re separated by at least one normal eating day.
What should I eat and drink during a fast?
During a fast, you can drink water and other calorie-free beverages, such as tea or black coffee. Many people also drink bone broth, which contains nutrients that support your body during a fast. Drinking liquids also help counteract fatigue and curb hunger.
If you’re following an intermittent fasting pattern that involves restricting your calories on fast days, you should focus on low-calorie, high-protein and high-fiber foods that will help you stay full.
What should I eat when I am not fasting?
Even when you’re not fasting, it’s still important to monitor how many calories you consume and choose healthy foods. Overeating during your non-fasting periods could interfere with the benefits of fasting and may even lead to weight gain.
Is intermittent fasting safe?
Intermittent fasting is one of many tools that can help you achieve your health goals, whether they include losing weight or controlling insulin levels. When done correctly and safely, intermittent fasting can help reduce your overall calorie intake and may lead to weight loss. However, intermittent fasting isn’t for everyone.
Before you get started, check with your healthcare provider to make sure intermittent fasting is a safe option for you. You shouldn’t try intermittent fasting if you:
- Have low blood sugar
- Are pregnant or nursing
- Have a history of eating disorders
- Are underweight or at a normal weight
If your doctor says intermittent fasting is safe for you, it’s a good idea to consult a registered dietitian about an intermittent fasting plan. A registered dietitian can help you develop healthy, sustainable eating patterns and provide guidance about the foods that will provide the fuel your body needs.
During intermittent fasting, it’s important to pay attention to how you feel. You may feel hungry and a little weaker than normal at first, but you should adjust your eating pattern and talk to your healthcare provider if you experience extreme hunger, feel faint, or develop other symptoms such as headaches every time you fast.
Intermittent fasting can be customized to fit your unique needs. However, combining it with a healthy diet and exercise will help you achieve your fitness goals sooner. And, just as with any lifestyle change, it’s important to approach intermittent fasting with a healthy attitude and seek guidance from a qualified healthcare provider.
To schedule an appointment with a Virtua registered dietitian, call 1-888-847-8823.
Updated June 10, 2019
