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Intermittent Fasting Can Lead to Muscle Loss, But It Doesn’t Have to – Here’s Why

June 30, 2021

Recent studies have revealed that intermittent fasting can lead to the loss of lean muscle mass – a concern for some who follow the popular dieting method, particularly to “get in shape.”

To understand how accurate these claims are and what they mean for those who fast, we spoke with Melissa Wadolowski, RD, LDN, CHC, CDCES – registered dietitian at Jefferson Health – New Jersey.

How does intermittent fasting work?

Intermittent fasting refers to a patterned eating regimen in which you refrain from eating for some portion of the day. Two popular methods include the 5:2 method – restricting calorie intake to 500 calories, two days out of the week – or eating one (large) meal a day (OMAD).  

The research referenced here, however, is regarding time-restricted eating, where you eat during a daily 6- to 8-hour window.  This can often be too restrictive if followed strictly long-term, especially for women, who are more prone to hormonal disruption from fasting.  It’s recommended that females follow a longer eating window of 9-10 hours a day or restrict their fasting efforts to a few days a week, explains Wadolowski.  

What are the benefits?

“Intermittent fasting has shown to be helpful with weight maintenance, but even more significant are the benefits it yields for heart health, brain health, mental clarity, and longevity,” said Wadolowski.

Do you always lose muscle mass when you lose weight?

For the most part, yes – weight loss is comprised of the loss of both fat and muscle, says Wadolowski, so this research shouldn’t deter you from continuing or trying to fast. It’s a matter of minimizing muscle loss, rather than avoiding it.

What causes people to lose more muscle than fat?

Food: It’s not just about fasting. It’s about the quality and quantity of what we eat, says Wadolowski. “Lack of protein is a huge culprit when it comes to muscle loss. The body doesn’t store protein the same way it stores other nutrients, so, we have to eat it regularly. We can’t expect fasting to do all the work, if what we do consume isn’t well-balanced.”

Some may struggle to fit in a healthy amount of protein if their fasting window is too strict; a more lenient, longer window to space your protein out may be helpful, explains Wadolowski. “Additionally, how much protein you need is key to keep in mind. Protein is notoriously overdone. It should only account for around 15-25 percent of our daily caloric intake.”

Exercise (or lack thereof): A sedentary lifestyle can also lead to muscle loss, adds Wadolowski. Strength-training, in addition to aerobic activity, is key to maintaining and building muscle.

Experts recommend all healthy adults do strength-training exercises for around 30 minutes, two to three times per week. This may include lunges, squats, lifting weights, planks, or crunches. If you’re working from home, you can use household objects, such as soup cans, in place of free weights. It’s important to start slow to build up stamina, especially if you haven’t had a regular exercise routine in a while. Breaks (days off) are also necessary, to allow your body time to recuperate (if you overuse your muscles, you can damage them).

How can you reap the greatest rewards from intermittent fasting?

Practice mindfulness and listen to your body, says Wadolowski. Put in the effort to help fasting work for you long term. Continue to eat right – whole, nutrient-rich foods – and stay active. If something doesn’t feel right, or you feel you don’t have enough time in the day to eat, make a change. Fasting is time-restrictive, but you don’t have to approach it with a restrictive or extreme mindset; remember, weight loss is only one component.

“If we don’t lose sight of what our bodies need to grow stronger, it is very possible to minimize muscle loss, and even gain muscle, through intermittent fasting,” said Wadolowski.

How soon can you expect to see results?

Physical changes don’t happen overnight for anyone, but they can appear more quickly for some, says Wadolowski. Not only does everyone’s body work at a different pace, it’s also much harder to notice changes on your own body because you see it every day.

Try to find a concrete way to map your progress that doesn’t just involve stepping on the scale, suggests Wadolowski. “It may be trying on the same article of clothing every few weeks or taking a selfie. Whatever works for you – just don’t give up!”

If any health complications arise while trying intermittent fasting, don’t hesitate to reach out to your dietitian or primary care physician for help.

To read Wadolowski’s last installment on the benefits and dangers of intermittent fasting, click HERE. For more information on Nutrition Services offered at Jefferson Health – New Jersey, click HERE.