Good morning! If you’re new here (as many of you are, thanks to my friends at How to Money), I’m so glad to have you in the community! I hope you find this and every week’s article insightful and helpful in your journey of health.

And if you’re an oldie but a goodie, you’re absolutely just as welcome. Thank you for sticking around. I hope you continue to find value in every edition of Move to Improve!

(If this email was forwarded to you and you'd like to receive this weekly newsletter, sign up below!)

❤️‍🩹 Does Intermittent Fasting Cause Heart Disease?

I came across this article last week. It made some pretty bold claims for some pretty weak data. “Intermittent fasting linked to higher risk of cardiovascular death, research suggests,” the title reads.

Let’s have a chat about what constitutes good science and drawing conclusions.

The “analysis,” (note—not a study) came from a School of Medicine in China, but “has not yet been peer-reviewed or published in an academic journal.” First red flag. Many a research study/analysis is thrown out before it ever makes it through peer review and publication. Too often, methods are inadequate, variables are not controlled, or conclusions are unclear. Yet many of these “analyses” still make it to our headlines and news feeds. So that’s the first problem. Anything not peer reviewed or published should be approached with caution and skepticism.

Let’s define some terms they looked at. “Intermittent fasting” (IF) is a pattern of eating that has numerous definitions, but has nonetheless gathered buzz in recent years. In a nutshell, it’s any method that restricts the time you eat (your “eating window”) and lengthens your time not eating (fasting).

• Technically, this analysis looked at a sub-method of IF known as time-restricted eating (TRE).

• They compared a group who reported restricting their eating to less than eight hours a day to a group who had an eating window of 12–16 hours, the comparison group.

IF & TRE do have some benefits. While many have touted autophagy (self-cleansing) benefits of fasts, it’s probably unlikely that the body gets far into these processes after just 16 hours of fasting. 

At this point, the majority of research seems to point to IF’s and TRE’s primary dietary advantage being its assistance with caloric restriction. I.e. if you’re trying to cut calories and lose weight, it’s easier to do that if you only allow yourself to eat within a certain window of time each day. Might there be other benefits? Sure. But this is probably the primary mechanism for any improvements in health and/or body composition.

Many people have seen positive outcomes while on IF/TRE. Myself, my friends, and some family have had success at achieving goals through intermittent fasting. Some people also have reported feeling more awake, alert, and energized on this eating pattern. My Master’s thesis was even about the subject, and whether or not resistance training workouts suffered if doing them while fasted vs. fed while IF. Spoiler alert—we didn’t find any negative effects!

So what’s up with this “study?”

Since many people have adopted an IF or TRE pattern of eating in the last decade or so, at least for a time, much research has been conducted on it. Ideally, this research is randomized control trials; those are the “highest quality” studies, where there’s a control group compared to the intervention group, and variables are controlled. But it’s also the hardest type of study to conduct, especially around nutrition. It’s just really hard to control what/how people eat for very long!

And that’s where we come to epidemiological and observational studies like this one. Much easier to conduct, but much lower quality evidence. There’s a trade-off. However, in the field of nutrition, these are often the types of studies we have to rely on. And you know from statistics 101 that correlation does not equal causation.

This study of 20,000 people utilized a just two days of food recall for their data. Imagine someone tapped you on the shoulder and said, “Here, please fill out this form. List everything you consumed the past 48 hours, including the quantity and timing of it.” Not many of us could complete that with much accuracy! This type of data is historically unreliable. 

Epidemiological and observational studies aren’t meant for us to draw conclusions from. At best, they’re meant to make us say, “Huh. That’s interesting. We should conduct some actual experiments around that and explore it more.”

The analysis “determined” that individuals condensing their eating window to eight hours or fewer had a 91% greater relative risk of dying from a cardiovascular event over the next eight years compared to the 12–16-hour eating window group. 

This is the first study to “draw conclusions” such as this, which should be a red flag in itself. Even the co-authors cautioned against making recommendations based on this research. But does the general public who reads the fear-mongering headline usually read that deep into it? Probably not. The headline is out there.

Some possible explanations

My first thought in terms of possible explanations was a classic chicken-or-the-egg scenario. The first natural conclusion to (prematurely) draw might be, “Oh! Intermittent fasting must cause—or at least increase your risk for—heart disease!” However, just as likely, and still not the only other option, is that people who are unhealthy already (overweight/obese, diabetic, already at high risk for heart disease, etc.) may be more likely to try IF/TRE methods of eating/dieting. 

• Think about it. If someone is concerned about their weight/health, there’s a decent chance they’re trying to do something about it. As IF has been touted as one of the easiest, most approachable ways to lose weight and improve health, there’s a pretty good chance that people are trying it…

• at least compared to the group eating for 12–16 hours per day who is perhaps less concerned with their dietary intake/timing. Maybe it’s a chicken or egg problem. We don’t know!

Not to mention, this analysis (or at least what has been presented and covered) presented no other outcomes. No other data around if IF/TRE eating patterns possibly improved outcomes or markers of health.

Additionally, these two “groups” weren’t really even comparable in the first place. As Dr. Peter Attia notes in his criticism on Instagram, “there were significant differences in the group sizes, other lifestyle habits, and comorbidities, making it almost impossible to compare the two groups.”

So let’s think—what actually causes cardiovascular disease and death? We pretty much know the mechanisms at this point: A heightened state of inflammation, stress, and poor health. Low cardiovascular fitness. A diet high in sugar, starch, saturated fat, and ultraprocessed food. That’s the lion’s share of what ultimately leads to the types of cardiovascular disease we see today. A pattern of excessive intake (consumption) and insufficient output (movement).

Does intermittent fasting align with any of these mechanisms that cause heart disease? Well not really. Typically, people who are practicing IF are improving their health—unless they threw all dietary quantity and quality to the wind since they felt like IF was a cheat code where they could eat whatever they want and lose weight. But most people utilize IF, alongside other lifestyle changes, to improve their health. That doesn’t really align with the mechanisms we know cause heart disease.

This isn’t to discount the analysis. It’s interesting, for sure! One possible contributing factor could be the stress of it all. Especially if someone is new to this eating pattern, it could be a stressor on the body. Perhaps it elevates their cortisol. In the wrong person at the wrong time, adding this extra stressor on top of their already stressful life could indeed lead to adverse events. 

Where do we land?

So after all this, where do we (I) land on IF and TRE? I wouldn’t be afraid of it. I think it can be beneficial for the right person—particularly someone who would be healthier if they could, for a time, reduce their caloric intake to achieve a healthier weight. Especially if that person struggles with eating excessively either early or late in the day. But that’s for them to discuss with their doctor/dietician.

My primary concern with IF is not about the risk for heart disease, but rather about inadequate protein intake. A large proportion of people are already not eating enough protein for good health every day.

• Because IF is a blanket caloric restriction across all macronutrients (e.g. unlike low-carb or low-fat diets that are focused on just one macronutrient), there is a risk of significantly cutting an already-inadequate protein intake.

• We cannot ignore muscle’s and protein’s role in health and longevity. Therefore, IF is probably not an optimal strategy to increase or maintain optimal protein intake that results in the subsequent health benefits that follow.

Long story short: Be skeptical of sensationalized headlines. Read into the details. Or stick around and read Move to Improve, where I can help you do that. 😉 

If it seems too good—or too bad—to be true, it probably is. 

✅ Take Action

Every newsletter's Take Action section will invite you to take small steps to improve your health. Recognizing that we all have different capabilities, I'll offer three different levels of action you can choose to take.

Level 1: Read the article in NBC News. What stands out to you? Do you have any questions?

Level 2: What other headlines of “myths” have you believed because of a sensationalized headline or blanket statement. Take a moment to consider your other fringe beliefs around health and fitness and evaluate whether they are evidence-based.

Level 3: Be a scientist and experiment on yourself! Obviously it’s hard to run a self-experiment that assesses your 8-year risk of a cardiovascular event. But on a much smaller scale, this is something you can do with everyday habits—especially if you get regular physicals or biomarker checks!

This newsletter is brought to you by… me!

Interested in becoming a sponsor? Know someone else who might be? I’d love to get to know you and/or your business and see how we can partner together. Reply to this email!

✍️ Drew's Picks:

• Listen & Learn: You may have signed up for How to Money’s newsletter last week, but have you listened to their podcast yet? Three episodes a week of awesome personal finance content.

• Wear: I recently bought a tee from Goodpark and love it! Check them out, 10/10 recommend with no financial incentive.

If you made it to the end of today’s newsletter, pat yourself on the back! And stand up and stretch. It was a long one, but I hope it helped you think critically.

As always, if you enjoyed this, please copy the link below and share with a friend!

Keep moving,

Drew

The content in Move to Improve is meant to be informative in nature, but it should not be taken as medical advice. It is always a good idea to consult with a trusted health professional before making any major lifestyle changes that could have a significant impact on your health. This is not a medical resource, and any opinions and articles are not intended for use as diagnosis, prevention, and/or treatment of health problems. They are not substitutes for consulting a qualified medical professional. Please think critically and take what I say with a grain of salt (aka don’t sue me).