Why everyone is talking about "fibermaxxing"

I don’t normally advise taking medical advice from TikTok but sometimes the algorithm gets it right and boosts a tip with actual evidence behind it like “fibermaxxing.” 

Don’t let the name turn you off. Fiber is a macronutrient with extensive research behind it, something that makes it unique in the grand scheme of nutritional science. 

We know that fiber is essential for: 

✅ Gut health (fiber is fermented by gut bacteria into short chain fatty acids including butyrate, which lower inflammation)

✅ Blood sugar regulation (fiber reduces postprandial glucose spikes, reducing your risk of metabolic syndrome) 

✅ Reducing cholesterol (fiber binds to cholesterol in the gut, reducing absorption and improving lipid profile)  

✅ Removing forever chemicals (fiber binds to chemicals including PFAS, reducing absorption and helping you flush them out) 

My personal fiber guideline: 30g is a good day, 50g is a great day. One of the ways I’m going to get there is by, can’t believe I’m saying it, fibermaxxing.

Today, on average, 50% of our calorie intake is from carbs but the majority of that—42% of total calories (or 84% of our total carb intake)—is not from fiber but from refined carbs, which have been shown to accelerate the aging process by damaging DNA (through increased oxidation) and by fueling disease processes like diabetes.

I was excited to see a new study published this month in the Journal of the American Medical Association adding more clarity to how you can incorporate fiber to optimize your health and help you age well. 

Using data from a cohort of over 47,000 women from the long-running Nurses Health Study, the researchers found: 

🫛 Good Carbohydrates reduce chronic disease.
Women with a higher dietary fiber intake aged better. Every 10% increase in daily calories that came from high-quality carbs in the form of whole grains, fruits, and veggies increased the likelihood of aging without chronic disease or significant mental or physical impairment by 31%.   

🍞 A carb-to fiber ratio of 5:1 or less is ideal.
To get the benefits of good carbs, aim for a low carbohydrate-to-fiber ratio of 5:1 or less, meaning for every 5 grams of carbohydrates there’s at least 1 gram of fiber. 3:1 or 2:1 is even better. Nutrition labels will give you total carbs and total fiber, so this is easy to measure on the fly. If there is no label but you’re eating a head of broccoli or a whole apple, you can be assured you’re in the right zone.

🥑 Replace refined carbs with fiber-rich fruits.
In addition to adding fiber to your daily calorie intake, replacing refined carbs with fiber increased the odds of healthy aging by 7-16%. Fiber from fruit had the biggest impact (14% increase in odds of healthy aging). Five fruits with excellent carb-to-fiber ratios: avocado, raspberries, blackberries, strawberries, guava.  

🧁 Use a CGM to find out which carbs spike blood sugar. 
We all know to avoid ultraprocessed foods but even whole grain fiber or fruit can produce a different glucose response in different people due to differences in genetics, microbiome composition, and even pace of eating. Learn how your body responds by using a CGM to track your blood glucose response to specific foods. I often prescribe the Freestyle Libre 3.0 to patients who then work with our health coaches to optimize meal planning based on the data. (Lingo and Stelo are two CGM options available without a prescription.)  

But, can you eat too much fiber?

Short answer: Yes. Taking “fibermaxxing” to the actual max can cause digestive issues like bloating, gas, and cramping in the short term and lead to nutrient malabsorption that can cause bigger issues. 

Aim for 10-15 grams of fiber per meal, and 5-10 grams per snack. Right now I’m adding a scoop of Sakara’s Fiber Super Powder to my smoothies to help meet my fiber goals. (I also like Metafiber from Metagenics.) 

Drink adequate amounts of water so you don’t get bloated. Aim for 12-20 oz of water with each meal, especially if you’re fibermaxxing. 

Commit to cooking one high fiber meal a day at home. If you’re looking for inspiration, my friend Mikaela Ruben’s veggie forward cookbook Eat to Love comes out today! I also follow Jesse Krux for simple plant-based meal ideas.

What I’m Reading This Week

#1 Can magnesium improve your blood sugar?

As if you needed more reasons to love magnesium! It's important for brain health, heart health, bone health, and for calming the nervous system. That’s why it’s one of the top supplements I recommend for women’s longevity. 

I was excited to see this recent meta-analysis further defining the benefits of magnesium for blood sugar control. Magnesium supports insulin production and insulin receptor function and also promotes glucose uptake into cells. This combination contributes to the author’s conclusion: a diet high in magnesium can lower the risk of metabolic syndrome by 21%.

Given magnesium’s association with a reduced risk of chronic conditions like type 2 diabetes, heart disease, and stroke, I recommend taking a magnesium supplement of 300-400mg per day. 

The best forms are:  

• Magnesium glycinate (like the one we make at Parsley, which I take nightly) for combating stress, aiding sleep, and boosting glutathione. 

• Magnesium threonate for cognitive enhancement, slowing brain aging, and reducing anxiety. Mag threonate has been shown to penetrate the blood-brain barrier best. But pro tip: I find mag threonate gives me crazy dreams, so I prefer glycinate personally.  

#2 What the new COVID vaccine recommendations mean for us

Last week RFK Jr. announced that the U.S. government would be ending COVID vaccine recommendations for two key groups: pregnant women and healthy kids. Then on Friday, the CDC contradicted Kennedy, saying kids can still get the vaccine after consulting with a doctor. 

In light of the extreme amount of noise happening around this topic, here’s my view on what you need to know when making decisions for yourself and your family: 

Before we break out our pitchforks and torches on this topic, I want to acknowledge that I know we all have strong feelings about this. The pandemic experience and the resulting fear it caused (whether the fear of getting sick, or the fear of another lockdown) lives in all of us, regardless of our politics. 

So take a breath, and let’s take a moment to look at the science. 

• COVID hospitalization rates are at an all-time low. So are COVID deaths; there were less than 250 weekly COVID-related deaths this month (compared to close to 1,000 per week in May of 2023). 

• Data from the 2024-2025 COVID season showed the booster further decreased the risk of hospitalization (vaccinated adults were 33% less likely to end up in the hospital or urgent care). The booster does not reliably prevent infection, it just reduces the severity of infection when it happens. 

• The risk of healthy kids (meaning kids without underlying conditions like diabetes, asthma, or obesity) being hospitalized with COVID was always low: less than 3 in 100,000 at the peak, the majority of whom had underlying conditions. (When COVID happened I had a 3-year-old and a 6-week-old and as mounting evidence showed that largely young kids were not dying from it, I thanked the universe every day). 

• On review of the 2024-2025 flu/COVID season, kids accounted for just 4% of hospitalizations and 59% of those had at least one underlying condition. (Kids under four are the most likely to be hospitalized with babies under 6 months having the highest risk.) 

The recommendation when it comes to pregnant women is more complex. 

• The ACOG (American College of Obstetricians and Gynecologists), representing the doctors responsible for caring for our pregnant women and delivering our babies, are strongly opposed to RFK Jr.’s decision to no longer recommend the vaccine, which I think is important to register.

• At the start of the pandemic 31% of pregnant women with COVID were hospitalized vs. just 5.8% of non-pregnant women. The CDC no longer tracks how many pregnant women are hospitalized with the virus, but we know that the risk of negative outcomes (including death) is still higher. 

• Systemic changes during pregnancy (increased pressure on the lungs, higher blood sugar, higher circulating body fluid volume) make it harder to fight off infections and systemic inflammation. (This is why even healthy pregnant women are at higher risk of severe illness if they get the flu, for example.)  

• Another reason to consider a booster: babies under 6 months rely on maternal antibodies transferred from mom both in utero and then through breast milk to fight off disease before they develop their own immunity. And because hospitalization rates of kids with COVID is more frequent in babies 6 months or less, there is an additional rationale to continue recommending the COVID vaccine in pregnancy. 

What I do for myself, my family, and what I recommend: 

• I do not currently get COVID boosters as I have no underlying risk factors and am not regularly in contact with high-risk patients. I see patients via telehealth, and don’t work in a hospital setting. 

• I am comfortable not vaccinating my kids for COVID. They do not have underlying risk factors that would put them at higher risk of severe disease. They have also had COVID and not had severe symptoms. I respect that this decision is personal to you and your family; by sharing what I am comfortable with for my family based on the science I shared above, I am no way judging you for what is best for yours. 

• If you are someone with an underlying risk factor (e.g. a chronic disease including obesity, lung disease, diabetes, or cancer) or are over the age of 65, the vaccine is still recommended. 

• If you are pregnant, the risk of severe COVID remains higher than for non-pregnant women, but is still low overall. I recommend consulting with your doctor about your personal set of risk factors and whether it makes sense to get a booster. If the shifting recommendations result in gaps in insurance coverage, the vaccine runs around $200 out-of-pocket.

As always, this newsletter is for informational and educational purposes only and is not intended as medical advice. Always consult your healthcare provider before making any health decisions or changes to your treatment plan.