Intermittent Fasting (IF): magic hack for health and longevity or just skipping breakfast in a fancy way? Let’s dive in to see if there are any scientifically proven health benefits behind this popular trend.
So… What is Intermittent Fasting?
In non-buzzword terms, intermittent fasting means you don’t eat for a certain period of time. It’s less about what you eat and more about when. The most popular variations include:
16:8: you fast for 16 hours and eat during an 8-hour window
5:2: you eat normally 5 days a week, then barely eat for 2 days (fun!)
OMAD: you eat one meal a day (double fun!)
Now that we have the definitions out of the way, let’s break down what actually happens in our bodies when we fast:
- Short-term fasting (4-18 hours after eating): blood glucose starts dropping a few hours after a meal. Your body starts converting glycogen into glucose (sugar) to use as energy. As glycogen stores start running out, your body will be looking for alternative energy sources. That’s when the fat cells start breaking down for energy, causing us to burn fat.
- Long-term fasting (18 hours-2 days after eating): as glycogen stores are depleted, you transition into “ketosis”, a process during which your body uses mostly fat as its energy source. At this point, cell clean-up crew kicks in, causing “autophagy”. It’s essentially your body’s way of Marie Kondo-ing dead and damaged cells. This is important as it could prevent some diseases and may promote longevity.
IF may lead to:
- Weight loss: you might eat fewer calories (unless your “eating window” becomes an all-you-can-eat buffet). Some studies have shown that IF has slight superiority over the good old calorie counting*.
- Improved blood sugar & heart markers: some research shows an improvement in insulin resistance, blood pressure and some inflammation markers**
2024 Study
Now for those of you who saw the 2024 study which linked IF to an increased risk of dying from cardiovascular diseases***, let’s look at that in a bit more detail.
This 8 year observational study of over 20,000 adults concluded that participants who restricted their eating to less than 8 hours per day had a 91% higher risk of dying from cardiovascular disease, compared to those with eating windows of 12–16 hours. Sounds scary, I know. BUT before we blame IF, let’s examine why the results may need to be taken with a pinch of salt.
- Study design: due to the study having an observational nature, we can only establish association and not causation.
- Other contributing factors: participants who had a super short eating window were more likely to practice a lifestyle which affected outcomes (poorer diet and less physical activity)
- Self-reported data: people may say they are doing IF while in reality they are skipping random meals due to various reasons.
Although there is sufficient scientific evidence showing that IF can be beneficial for our health, a word of caution to my fellow ladies. Women’s unique responses to IF are still severely understudied. There is some preliminary data which shows that time restricted eating could mess with our hormones and menstrual cycles****. Although the data comes mostly from animal studies, there is simply not enough research on human subjects. Personally, I was hangry and did not have energy to exercise when I tried IF so it’s not for me. Be gentle and always listen to your body and please STOP if you notice any changes to your cycle.
Verdict
Current scientific evidence shows that IF can support metabolic health, weight loss and improve blood sugar control. However, the data on the effects on females is inconclusive and understudied so caution should be taken.
* Intermittent Fasting versus Continuous Calorie Restriction: Which Is Better for Weight Loss? – PMC
**Intermittent Fasting: A Heart Healthy Dietary Pattern? – PMC
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