What's the Deal with Intermittent Fasting?

Here's what you need to know before you jump into IF.

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Intermittent Fasting (IF) is still wildly popular, but is slashing your food intake for extended periods of time the key to a healthy lifestyle? Here, our nutritionist weighs the pros and cons, so you can decide if this diet is right for you.

Intermittent Fasting Basics

IF can be practiced in a variety of ways. Methods can vary from fasting for full days at a time to fasting for extended periods over 24-hours. Alternate Day Fasting (ADF) involves one day on and one day off eating. Fasting days can vary from zero to 25% of calorie needs, so on fasting days you can eat very small amounts. Another popular IF pattern is the 5:2 regimen, where calories are restricted to about 500 calories on 2, non-consecutive “fasting” days and the other 5 days follow a normal pattern of eating. Time-Restricted Feeding (TRF) enthusiasts fast for 16 hours each day and only take in calories during the remaining 8 hours of the day, usually between 8 a.m. and 4 p.m. or 12 p.m. and 8 p.m.

Pros

The upsides to IF may impact several parts of the body and the mind.

Weight Loss

One of the most popular reasons people try IF is for weight loss. There is some research to support that certain methods of fasting may help with weight loss and reduced body fat. According to researchers at the University of Alabama, metabolism functions at optimum capacity in the earlier hours of the day. Researchers suggested that eating earlier in the morning would produce better weight loss outcomes. The 2016 study found that only eating between the hours of 8 a.m. and 2 p.m., followed by an 18 hour fast could reduce daily hunger swings and increase fat burning during several hours at night.

Exercise may also play a role. Another study found that subjects who were more active displayed better body fat loss when following a TRF regimen.

Brain Health

Intermittent Fasting may be beneficial for the body and the brain. A rodent study published in 2015 found that sticking to an IF protocol can help spark brain health, fight off inflammation and may prevent the age-related decline in brain function.

Cons

It’s not all positive findings when it comes to IF.

Limited Research

Much of the IF research to date has been done with lab animals. Many of the human studies have very small subject populations. For both these reasons it’s hard to draw powerful conclusions about the effectiveness of IF, especially long term.

Side Effects

Let’s get real, skipping all those meals can potentially lead to side effects. Patients reports that day to day practical issues when on an IF plan may include hunger, headache and irritability. Stopping and restarting eating solid foods after long periods of time can also lead to GI disturbances including gas, bloating and constipation.

Red Flags

IF of any kind can be dangerous to folks on certain medication or with preexisting medical conditions. People with specialized calories and nutrient needs such as diabetics and pregnant and breastfeeding women should not adopt fasting lifestyles.

Dana Angelo White, MS, RD, ATC, is a registered dietitian, certified athletic trainer and owner of Dana White Nutrition, Inc., which specializes in culinary and sports nutrition.

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