From Atkins and Paleo to Keto and Whole30, there’s been no shortage of popular diet trends over the last several years. More recently, you may have heard of people fasting — completely abstaining from food during certain times of the day or not eating for 24 hours at a time.

Exactly why has it become such a big deal and is it safe?

We talked to Emily Bullard, a registered dietitian nutritionist at the Cardiac and Vascular Rehab program at Texas Health HEB, about her thoughts on the newest health trend and what researchers are saying.

“So far, we’re hearing that intermittent fasting can help reduce insulin spikes, is cardio-protective and may promote resiliency of the immune system, in addition to weight loss,” she explains. “It may also reduce LDL cholesterol, triglycerides and blood pressure. Additionally, ketosis may occur and help to decrease one’s appetite on fasting days.”

So, while it seems promising and may be effective for weight loss in the short term, we’re just not sure about the long term because the research just isn’t there. And while a Google search returns articles about fasting from websites ranging from WebMD to Men’s Health, there could be a good reason it’s often referred to as a “fad diet.”

“When considering any new eating plan, I ask my patients if it’s something they think they can sustain long-term,” Bullard explains. “For example, I had one patient try fasting and he lost 10 pounds quickly, but as soon as he went back to eating regularly, he gained it all back. It may be appealing for some since no specific diet has to be followed, but strictly limiting yourself to when you can eat may not be effective for some people. This could be true especially patients with diabetes, hypoglycemia or those with underlying eating disorders, like binge eating.

“The main thing to consider is whether you can still eat a healthy diet and get the nutrients you need because you can’t just fast and then eat whatever you want. It only works if you practice good nutrition and achieve a calorie deficit.”

So how exactly does fasting work?

According to the Academy of Nutrition and Dietetics, people usually attempt fasting in one of the three following ways:

1. Alternate day fasting: rotating days between eating and fasting
2. Modified fasting: restricting caloric intake to 20-25 percent of daily needs, or a low amount like 500 calories; OR the 5:2 method, which is eating for 5 days and week and fasting for 2
3. Time-restricted fasting: limiting food intake to shorter windows of time, such as 8 hours when eating is permitted and 16 when it is not

An article published in the Canadian Medical Association Journal points to the distortion of facts that often occur when diet and exercise trends achieve mainstream popularity. When done properly, however, the author explains, fasting can lead to weight loss and potentially slow the progression of diseases such as cancer. (Most of the research on fasting has been conducted on animals, so it remains to be seen how many of the benefits translate to people.)

While the jury is still out on the long-term benefits and Bullard says more research needs to be done, she says intermittent fasting could be effective for some people.

“If you find yourself ravenous during the fast and tend to overeat during non-fasting times, you may not see progress with your weight loss,” she says. “The weight can come back very quickly if your meal timing becomes more erratic and you’re unable to stick to the timing requirements. However, if the fasting/eating pattern falls within your regular ‘rhythm’, you may find it effective and doable.

“Also, if you find yourself making better choices while intermittent fasting, then it may be a good fit. As always, it’s advisable to speak with your physician about underlying health concerns and if it would be recommended for you.”

If you’d like to speak to a physician about dietary changes, check our our physician provider page here.