In the hit Netflix series, You, a cheeky nod to a growing trend popped up in the third season.
Set at a child’s birthday party, one of the main characters offers her “free of everything” cupcakes to some guests. “I’ve already hit my macros,” says one. “I’m fasting,” says another.
The blink-and-you’ll-miss-it joke about intermittent fasting–and the type of person who practices it–was good for at least a smile.
Intermittent fasting isn’t new, but it entered mainstream consciousness when it was focused on in an episode from another Netflix show, (Un)Well, a docuseries about the pros and cons of various health practices. Die-hard proponents cite weight loss, more energy, and improved mental well-being as reasons for their efforts.
So what is it?
Simply put, intermittent fasting means limiting your eating to certain hours of the day. The most popular schedule is a daily one: 16/8, meaning you fast for 16 hours and eat during the other eight. There is also a weekly fasting sked, or 5/2, meaning you eat normally for five days and fast for two days (limiting your diet to 500 calories each day).
If you’re looking to lose weight, intermittent fasting has proven successful for many. But there are other reasons people fast; the main one is a boost to the way your body functions (thanks in large part to how fasting interacts with your hormones).
While there may indeed be benefits, there are also risks involved. So let’s break it down.
The main benefit of intermittent fasting is how it acts on metabolic function, hormones, and insulin production. Put simply, when we restrict the hours that we eat (especially not eating during the evening and before bed), we give our body a break from digesting and, specifically, from converting sugar to energy. When we aren’t eating, not only are we reducing the number of calories that enter our body, but we’re giving our cells time to do their job, especially the pancreas, which secretes insulin to deal with the sugar and carbs we all love to eat. No sugar going in means the pancreas can take a break, and our cells can focus on flushing the toxins already there.
A brief rundown of the pros include:
- Fasting impacts your hormones, especially insulin production (which lowers blood glucose levels)—Human Growth Hormone increase, leading to fat loss and increased cellular repair.
- It gives our bodies a chance to cleanse and detox.
- Boosts metabolic function and therefore burns more calories, leading to weight loss and even the loss of visceral fat (the harmful fat that builds up in the abdomen).
- Your pancreas gets a break. Since sugars aren’t coming in as often, the pancreas doesn’t need to produce as much insulin to break it down. Reducing blood glucose levels means no need for your pancreas to produce insulin, letting your body rest.
- It can decrease inflammation and the body’s susceptibility to free radicals (which contribute to aging).
- Several studies have shown a positive relationship between fasting and heart health, but these studies involved animals only, so more research is needed.
- It might help with cellular repair and your cells’ ability to remove waste, meaning protection against things like Alzheimer's and some types of cancer.
- Because of the metabolism boost that results from fasting, many anti-aging proponents argue that intermittent fasting can lead to a longer life. However, studies have only been conducted on animals, and while the results are encouraging, human trials are necessary.
Reasons to Be Wary
As mentioned above, many of the studies that people use to support the benefits of fasting have only been done on animals, so we don’t know the full extent of how it affects humans.
We know some people should NOT be fasting. For example, if you are at risk for or have a history of disordered eating, are under 18, or are pregnant or lactating, you should stay away from fasting. And while fasting can help decrease blood glucose levels, fasting generally isn't recommended if you have already been diagnosed with diabetes.
Also, some people who fast find that they over-focus on the clock or become irritable or anxious during fasting periods.
Healthy eating is always key. Some may think that they can eat whatever they want during eating times because they're fasting. Not so. Choosing healthy foods–lots of fruits and veg, whole grains, lean protein, and lots of water–remains essential.
Low blood sugar can leave you feeling tired and weak. It can also prompt sleep disruptions, and some research has shown that fasting can lead to muscle loss.
Gender May Play a Role
If you’re a woman, there may be a reason to think twice before giving fasting a try. Due to its effect on hormones, women may be affected more acutely.
Mood swings, missed or irregular periods, and, in extreme cases, fertility issues can be linked to hormonal shifts and stressors to the body (of which intermittent fasting is one). If you are already highly stressed, adding fasting to the mix can be too much for the body to handle.
Lastly, research on blood sugar suggests that this effect only holds true for men and that fasting made blood sugar levels worse in women.
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