I'm sure you've heard all the buzz in the past few years about the wonders of intermittent fasting.
You've probably heard appealing promises like...
It's great for longevity!
It prevents signs of aging!
It's fantastic for weight loss!
But you can't help but wonder... is it just another passing fad or a new essential in your nutrition arsenal? Is it right for you? What are the pros and cons? Which schedule is the best? Does it actually work for weight loss?
We're going to answer all that and more in today's episode so you feel confident whether you decide to take it or leave it.
What Is Intermittent Fasting (IF)?
Simply put, IF is where you eat at certain intervals and you don't eat at certain intervals. How long those intervals last varies from plan to plan.
There's the 5:2 diet where you eat normally for 5 days and then eat very little (500-600 calories) for 2 non-consecutive days.
There's alternate day fasting where you don't eat every other day.
There's time restricted eating where you fast and then eat at specific intervals like 12:12, 16:8, or even 20:4 respectively. (The minimum requirement for a true 'fast' where you shift from using external sources of fuel to internal sources is 8 hours.)
There are also fasting mimicking diets where you eat in a way that supposedly gives you the benefits of fasting by blocking the pathways that prevent the benefits of fasting.
Though most of the studies supporting this have only been done on animals, so more studies need to be done to confirm the benefit in humans.
Another form of fasting mimicking is where for a week you eat 50% of your normal calories, and then for 3-4 weeks you eat normally.
As you can see, there are lots of options to choose from which may be causing you to ask...
Which version is best?
The IF approach that will work best for you is going to be determined by a number of factors: your age, sex, health, preferences, lifestyle, schedule, and more.
For example, men can do more strict versions than women. People who are stressed should take a gentler approach. People with a history of eating-disorders should approach with caution. People who are uncomfortable feeling hunger should do shorter periods of fasting. People who workout less can tolerate fasting better than avid exercisers.
2 rules of thumb to help you decide:
1. Experiment, but start slow. You may think the more extreme the better, but many people actually see more benefits and fewer drawbacks with a gentler approach like skipping a meal here or there instead of committing to a day of no food.
2. Listen to your body. You may here a million experts saying a 16:8 schedule is the way to go, but if after 16 hours of fasting you feel starving, light-headed, moody, and fatigued or if it sets you up to overeat, guess what? It doesn't work for you. Period.
What Are the Pros?
Before we jump into the seemingly miraculous benefits of IF, keep in mind a few things:
1. A lot of the research supporting IF has been done on animals, not humans.
2. When compared to a control group of people on the Standard American diet, almost any change will show benefits.
3. IF usually causes us to eat less leading to weight loss which makes it hard to tell whether the benefits are from the timing of meals or simply from getting to a healthier weight.
With that being said, let's dive in...
"Recent research shows that, when done properly, IF might help:
Fasting also stimulates many cellular and molecular mechanisms that our bodies use to thrive in conditions of food scarcity. Blood sugar, insulin, resting heart rate, and blood pressure all decrease - while insulin sensitivity and cell clean out (called autophagy) improves." -Precision Nutrition
By going for at least 8 hours without eating, our body is able to stop metabolizing food and start metabolizing "zombie cells" (old cells that resist beneficial death and release pro-inflammatory, tissue-damaging chemicals). When we can metabolize these zombie cells, we help slow down signs of aging by preventing the damage and inflammation they cause to surrounding cells.
Finally IF can be a tool to help you understand and tolerate hunger. Kind of like exposure therapy, if you have a fear or an anxiety around feeling hungry, IF can be a way of proving to yourself that hunger is just a feeling and that it isn't going to hurt you. It can also help you understand what true hunger feels like if that's a skill you struggle with.
What are the cons?
1. While men tend to do pretty well with various forms of intermittent fasting, women's bodies pose a different challenge.
The hormones that help regulate our cycles, metabolism, and mood are very sensitive to fluctuations in our energy intake.
Simply put, when we go longer stretches without fueling ourselves our bodies have a bit of a freak out that can cause lasting issues.
For example, fasting can disrupt the release of gonadotropin releasing hormone which is responsible for telling your pituitary gland to release luteinizing hormone and follicular stimulating hormone which stimulates the production of estrogen and progesterone. When this whole system is disrupted it can prevent you from ovulating or getting your period.
Not to mention, altering your estrogen can negatively impact your brain function, mood, gut, recovery, appetite, metabolism, and fat storage.
2. "One 2005 study published in Obesity Research tested eight men and eight women, all non-obese, who were instructed to fast on alternate days for a period of three weeks.
After the three weeks, men had improved insulin sensitivity, and their glucose response was unchanged.
The women, however, showed no change in insulin response, but their glucose tolerance was slightly worse than it was before the experiment started." -Precision Nutrition
3. Just like working out is a stressor, fasting is a stressor. So you can over-do it especially if you're experiencing stress from other sources. Taxing your system this way can cause a ripple effect that down-regulates your thyroid and disrupts your adrenals.
4. The eating patterns of IF can mimic the binge/restrict patterns of disordered eating. If this is a cycle you already struggle with, IF may not be the best call for you.
5. Skipping meals can lead to overeating later.
6. IF fundamentally teaches you to ignore your body's hunger cues in order to adhere to a set of dietary rules.
7. Your exercise performance may suffer, especially at the beginning.
Things to Remember About IF
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