Does Intermittent Fasting Work? The Data for 5 of the Most Popular Claims

concept of intermittent fasting and ketogenic diet, weight loss.
Intermittent fasting is an increasingly popular choice among those looking to improve their dietary health. So does it work? And how?

What is Intermittent Fasting?

Intermittent fasting is the practice of abstaining from food for predetermined periods of time. Some practitioners will opt for a day or more of consistent fasting while others may relegate fasting to a particular time of day.

Periods of fasting during a single day regularly range from 12 to 16 hours. During this time, only water is allowed (and sometimes tea of coffee). These partial-day schedules are frequently referred to as time-restricted feeding.

Benefits of Intermittent Fasting

The practice is thought to have several health benefits. In this article I’ll go through the most popular benefits of intermittent fasting and explore the evidence to answer the question: does intermittent fasting work?

Note that intermittent fasting is not recommended for those suffering from diabetes, as fasting can cause dangerous drops in blood glucose levels that diabetics cannot endure. Intermittent fasting is also not recommended for individuals who’ve suffered from eating disorders as it can trigger these behaviors again.

Weight Loss

For many individuals who take up intermittent fasting, this is the primary reason why. The’re trying to lose weight or maintain a healthy weight. So what does the evidence say?

The Harvard School of Public Health published an article reviewed over 40 different studies that seemed to support the idea that intermittent fasting was effective for weight loss.[1] They also found that like any other weight loss plans the dropout rate was about the same – in other words, people were no more likely to succeed or fail at weight loss than they would be at any other type of diet designed to drop pounds.

Fitness and weight loss concept

Also assisting in weight loss, intermittent fasting has been shown in a study published by The American Journal of Clinical Nutrition to increase metabolic rate through the increase of a hormone called Norepinephrine.[2] The study found that resting energy burn was increased during periods of fasting.

It seems the evidence is fairly unanimous that intermittent fasting can facilitate weight loss. In fact, after an exhaustive search for instances where intermittent fasting wasn’t effective for weight loss, all that I could find were examples of people who were either over eating during non-fasting periods or simply eating junk. So intermittent fasting is effective for weight loss, but you still have to eat responsibly when you’re not fasting or, just like any other weight loss plan, you will fail.

Improved Heart Health

Another popular reported benefit of intermittent fasting is that it’s good for heart health. Considering that maintaining a healthy weight is well known to be good for cardiovascular health, many of the pieces of evidence already presented can suffice to say confirm this is true. That being said, fasting does initiate other mechanisms aside from weight loss that are good for cardiac health.

According to a study published in The American Journal of Clinical Nutrition, people who fasted on alternate days not only confirmed our earlier point about weight loss, but those same subjects displayed lower LDL (bad) cholesterol and lower blood pressure.[3] Both of these are considered important markers for heart health.

Another study which looked at Muslims during the month of Ramadan found similar results. During Ramadan, Muslims neither eat nor drink from sunrise till sunset each day. This makes them an excellent study subject as the entire month of Ramadan is an extended period of intermittent fasting. The study conclusion stated that prolonged intermittent fasting seemed to reduce risk factors for cardiovascular diseases.[4]

So evidence does support the claim that intermittent fasting helps improve heart health and overall cardiovascular condition.

Cancer Prevention

It’s funny how pretty much every health fad or ‘power food’ out there seems to claim it helps prevent cancer. In fact, if you search hard enough, you can find an argument for just about every food in existence being a ‘cancer fighter’. So I tend to take these claims with a grain of salt unless there’s some real hard evidence.

Turns out, there really is evidence. In an article by The Osher Center for Integrative Medicine, they researched years’ worth of studies and found that intermittent fasting did indeed seem to help with cancer prevention.[5]

Even more interesting is also the existence of evidence showing that cancer patients who were fasting handled chemotherapy treatments better than those who did not.[6] Specifically, those who fasted had a lower toxicity after chemotherapy, which is critical for a cancer patient’s ability to complete a treatment regimen.

Just like the prior 2 claims, it seems that intermittent fasting does help prevent cancer and also helps those undergoing treatment.

Prevent Alzheimer’s Disease

In my opinion, diseases of the mind such as dementia and Alzheimer’s are utterly terrifying. Just the thought of losing my grasp on reality is enough to send me spiraling into a near existential crisis. So this claim is certainly very intriguing to me. So what do the studies say?

Senior woman playing jigsaw puzzle on wooden table at home

While the evidence for mental deterioration is not as cut and dry as those for weight loss, some studies do seem to show positive results. One study found that intermittent fasting help reduce memory loss in Alzheimer’s patients.[7]

It’s also worth nothing that even in the absence of a direct mechanism between fasting and brain deterioration, a significant risk factor for dementia and Alzheimer’s happens to be obesity. So it may turn out that intermittent fasting has an indirect effect on preventing such diseases by reducing the risk factors.[8]

Increased Lifespan

Any time I see a claim that something can make you live longer, I take it with a grain of salt. Not only are the frequently dubious, but they also are difficult to prove.

Studies have shown however, that calorie restriction in general can promote a more healthy aging of cells.[9] It still appears to be unclear whether this directly results in a longer life expectancy.

Final Thoughts on Intermittent Fasting

While not every claim regarding intermittent fasting is rooted in hard science, the evidence is clear that it’s an exceptionally good way to improve your overall health.

You start a regimen of intermittent fasting by starting off with just portions of the day for about 12 hours and then increasing that gradually to a 16-hour time period where you consume little to no calories. More advanced fasting may include going an entire 24-hour period without eating, just be sure you don’t over eat once you’re restriction time ends or you may sabotage your results.


Sources & Additional Reading

1. Harvard School of Public Health: Diet Review: Intermittent Fasting for Weight Loss

2. The American Journal of Clinical Nutrition: Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine

3. The American Journal of Clinical Nutrition: Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults

4. US National Library of Medicine National Institutes of Health: Interleukin-6, C-Reactive Protein and Biochemical Parameters during Prolonged Intermittent Fasting

5. Osher Center for Integrative Medicine: Cancer and Fasting/Calorie Restriction

6. Cancer Therapy Advisor: Intermittent Fasting and Cancer

7. US National Library of Medicine National Institutes of Health: Intermittent fasting protects against the deterioration of cognitive function, energy metabolism and dyslipidemia in Alzheimer’s disease-induced estrogen deficient rats

8. Cognitive Vitality: Can Intermittent Fasting Help Prevent Dementia?

9. The Harvard Gazette: Harvard study shows how intermittent fasting and manipulating mitochondrial networks may increase lifespan

Writer & Blogger

I'm an aspiring writer from Santa Monica, CA who writes about a little bit of everything. I love paranormal stuff, working out, nature, wildlife, and general humor.

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2 thoughts on “Does Intermittent Fasting Work? The Data for 5 of the Most Popular Claims”

  1. April, this is an excellent article with tons of great information. Thanks for putting it all together! I’ve been looking for some good solid information on the benefits of intermittent fasting for a while and this wraps it up nicely. Time to start my IF regimen!

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