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How to Lose Visceral Fat in 8 Weeks (Proven in RCTs) — Transcript

by Nick Norwitz MD PhD · 3,222 words · 534 segments · language en · Watch on YouTube

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0:00I need you to look at this green banana.
0:02Really look at it. It looks
0:03unappetizing, right? The kind of thing
0:05you just pass over at the grocery store
0:06without a second thought. But, hidden
0:09inside this green banana is something
0:11strange.
0:12What the heck is that? Something most
0:14people don't know about. It's called
0:16resistant starch. And the deeper I went
0:19into the biology of resistant starch,
0:20the more impressed I became. This isn't
0:23a fiber, but it's not your typical
0:24starch either, like in rice or pasta.
0:26It's a compound that reshapes the
0:28microbiome and can drive profound
0:30improvements in metabolic health,
0:31dropping weight, dropping body fat, and
0:34even dropping visceral fat as proven by
0:37MRI imaging. And best of all, the
0:40benefits are completely independent of
0:42caloric intake. Seriously, the science
0:45is compelling. The randomized controlled
0:47trials are undeniable. But, there's one
0:51really critical detail you need to
0:52understand if you want to translate the
0:55science [music]
0:55we're going to roll through into health
0:57improvements in your own life today. Let
0:59me show you the science, [music] and
1:01maybe, just maybe, you'll even want to
1:03bite into this nasty green banana.
1:08I'm scared.
1:10Resistant starch causes fat loss. It's
1:12much harder to digest. Participants
1:14literally excreted, pooped out, more fat
1:17and fatty [music] acids. Hundreds
1:18centimeters squared of visceral fat in
1:20eight weeks. Had a change in liver fat
1:22experienced on the order of 58%. That's
1:25huge. Some people had a 58% drop, and
1:27some people only a 7% drop. Why?
1:30So, this video is going to have five
1:31chapters. In chapter one, I'm going to
1:33go over what resistant starch even is
1:35with a fun little demo. In chapter two,
1:38I'm going to cover resistant starch
1:39causes fat loss in humans. We're going
1:41to jump into a randomized controlled
1:43trial, powerful data clearly
1:45demonstrating that resistant starch
1:46drives weight loss, fat loss, and even
1:49visceral fat loss in humans as proven by
1:52MRI imaging, and all in a calorie
1:54independent manner. Then in chapter
1:56three, we're going to go over mechanisms
1:58of action. If you've gotten to know me a
1:59little bit, you know this is my
2:00favorite. How this works in the body,
2:02what is the biology, what is the
2:04physiology, and we're going to explore
2:05additional benefits beyond weight loss.
2:07>> As a quick sidebar, people have been
2:09asking if I use AI to write the
2:11mechanisms breakdown papers as proof
2:13that that's not the case.
2:15Uh, here are some of the printouts.
2:17Sorry, trees. And I love to take notes
2:20with hand sketches.
2:21Those are just a few, so
2:23no, the mechanism breakdowns are only
2:25me, not AI.
2:26>> Then in chapter four, we're going to
2:27talk about responders and non-responders
2:31to resistant starch. We're going to move
2:32beyond group averages and examine why
2:36some people respond really well to
2:37resistant starch and others are low
2:39responders or non-responders. What
2:41differentiates people? And how can you
2:43use this in your own life, which brings
2:45us to chapter five, actionable insights.
2:47Where to start and how to apply the
2:49science in your own life. We're going to
2:50build to that. As always, you can find
2:52more details, a written walkthrough, and
2:54early access to breakdowns like these
2:56and much more at
2:57statecuriousmetabolism.com,
2:58our best-selling science newsletter. And
3:00a quick, sincere thank you for helping
3:02make it such a spectacular oasis of
3:04nuance on the internet. Thank you. With
3:06that, let's get to chapter one. What the
3:08heck is resistant starch anyway?
3:11Well, chemically, starch is just a chain
3:14of glucose molecules linked together.
3:16That's it. And under normal
3:18circumstances, enzymes made by your
3:20body, like salivary amylase in your
3:22saliva and pancreatic amylase released
3:24by your pancreas, break down starch
3:26efficiently into glucose molecules.
3:28Those glucose molecules then get
3:29absorbed in your small intestine and
3:31become readily available carbohydrate
3:34energy. Fast, efficient,
3:35straightforward. That's how carbs and
3:37starches are digested. But, enter
3:40resistant starch.
3:47There are many different types of
3:47resistant starch, but we're going to
3:49focus on type two resistant starch
3:50because that's what the studies we're
3:52about to review examine.
3:56Type two resistant starch is highly
3:58crystalline. The glucose chains are
4:00arranged in such a way that your
4:01digestive enzymes just can't easily
4:03access them. And during the demo, think
4:06of it not as a green banana, but like a
4:07bundle of raw spaghetti taped together.
4:10It's still spaghetti, same material, but
4:12because it's tightly packed and rigid,
4:14it's much harder to digest. That's
4:16resistant starch. And I know I'm not
4:17going to try to eat this, but it's the
4:18same chemistry, different architecture.
4:21So, it resists digestion in the small
4:23intestine, evades your body's enzymes,
4:26and travels to the colon. And this is
4:28where the next question popped into my
4:30mind while I was reviewing these data.
4:32If our enzymes can't break down
4:34resistant starch, how can bacteria? And
4:37here's the nuance. Our bodies have a
4:39limited set of starch-digesting enzymes.
4:41We can't digest this, but gut bacteria,
4:43on the other hand, they produce dozens
4:46of carbohydrate-active enzymes. They
4:47have a greater diverse set of tools to
4:50autonomously separate out the strands of
4:53spaghetti and process them. So, once
4:56resistant starch reaches the colon,
4:58bacteria can slowly erode these tightly
5:00packed crystalline structures and
5:02ferment them. This is how it changes the
5:05microbiome and causes the microbiome to
5:08restructure, produce different hormones
5:10that communicate with our bodies, get
5:11into our bloodstream, and change our
5:13biology. This is how resistant starch
5:16works, which brings us to chapter two,
5:18resistant starch causes fat loss. Let's
5:21begin with the first of our studies,
5:22published in Nature Metabolism. This was
5:24a randomized controlled crossover trial
5:27involving 37 men and women with BMIs
5:30above 24.
5:31A crossover design means each
5:33participant served as their own control.
5:35Everyone [snorts] completes two phases,
5:37a resistant starch phase where people
5:39consumed 40 g per day of resistant
5:41starch and a calorie-controlled control
5:44starch phase. Each phase was eight weeks
5:47with a four-week washout period between.
5:50This was an especially rigorous study as
5:51well because the participants'
5:52background diets were controlled. And,
5:55even more importantly, the study was
5:57double-blinded.
5:59So, to quote from the paper, to quote
6:01the authors, "Resistant starch and
6:03control starch were packaged in
6:04identical sealed bags with an identical
6:07appearance, and participants and
6:09investigators, the researchers, were
6:11blinded to the group allocations during
6:14the double-blind period." So, this
6:16design effectively eliminates placebo
6:18effects, controls for calories, and
6:19minimizes experimental bias. In short,
6:22this was an exceptionally well-designed
6:24study, very rigorous. Now, during the
6:27resistant starch phase, body weight
6:29decreased significantly compared to both
6:32baseline and the control diet phase.
6:35Plus, fat mass also declined with a
6:38specific and meaningful reduction in
6:40visceral fat mass. That's the
6:42inflammatory fat that surrounds your
6:43internal organs and drives
6:45cardiometabolic diseases. Now, in
6:47addition to the numeric values, I want
6:49to show you representative MRI images so
6:51you can see the raw data signal for
6:53yourself. You can see here the before
6:55and after of the abdominal cavity of
6:57people sliced like a loaf of bread. And
7:00in just eight weeks of resistant starch
7:02supplementation, you can see there's a
7:04substantial reduction in the red, the
7:05visceral fat in human abdominal cavities
7:08proven by MRI. How cool is that? And,
7:11congratulations, you're now a
7:13radiologist. But, let's move forward.
7:14Let's get to deeper nuances. When you
7:16look at the data spread, you'll notice a
7:19lot of individual variability. Some
7:21participants experienced a modest but
7:23still significant reduction in visceral
7:24fat, while others had dramatic
7:26responses. One individual saw a decrease
7:29of 100 cm² of visceral fat in eight
7:33weeks. That is a huge change in a short
7:36time frame. Now, to tease you a little
7:38bit, we're going to discuss why some
7:39people respond more strongly than
7:41others. So, move to the edge of your
7:43seat with your bucket of resistant
7:45starch popcorn in hand, if that's a
7:46thing, someone please tell me, go Google
7:48it, and if it's not a thing, I hope
7:50somebody invents it. But that aside, the
7:51benefits didn't stop there. Resistant
7:54starch also improved insulin
7:56sensitivity, reduced inflammatory
7:58markers like TNF alpha, improved levels
8:01of proteins involved in lipid
8:02metabolism, and even increased fecal
8:06lipid excretion. Yes, participants
8:08literally excreted pooped out more fat
8:11and fatty acids. That's pretty crazy,
8:13but it gets crazier as we get into
8:15chapter three, the mechanisms of action.
8:17This is the fun part, at least for me
8:20and you as scientists, less so for the
8:22mice involved in the experiments we're
8:24about to discuss, because the
8:26researchers performed fecal microbiota
8:28transplants, FMTs, using stools from
8:31human participants either after the
8:33resistant starch or control starch
8:36interventions. These samples, these poop
8:38samples from people, were then
8:40transplanted into mice who have had
8:42their microbiomes wiped out with
8:44antibiotics.
8:45The goal here is to establish causality.
8:49In other words, if we transfer the
8:51microbiome conditioned from humans who
8:53consumed resistant starch or control
8:55into mice who are all maintained on the
8:58same diet, can we reproduce the
9:00benefits, the metabolic benefits
9:02observed in the humans?
9:04And here's what they found.
9:06Mice that received a microbiota
9:08transplant, the fecal transplants, from
9:10humans fed resistant starch as compared
9:12to control, mice lost body weight and
9:16lost fat mass within just two weeks
9:18despite identical diets. By the way, and
9:21as a quick aside in the newsletter, I
9:23also show images of the dissected
9:24animals, so you can see literally inside
9:27their abdominal cavities, but I didn't
9:28want to jump scare you with the graphic
9:30images on YouTube. I also didn't know if
9:31YouTube would ding the images. So, go to
9:33the letter if you have a strong stomach.
9:35Oh, and on that, that reminds me, strong
9:38stomach, in the letter I also explain
9:40how resistant starch may help heal leaky
9:42gut. This goes so far beyond calories,
9:45but let's step back. In summary,
9:47all of this that we've reviewed suggests
9:49resistant starch supplementation can
9:51drive meaningful fat loss, including
9:53visceral fat loss, as demonstrated by
9:56MRIs in humans in a double-blind
9:57placebo-controlled trial, and that these
9:59changes are mediated by changes in the
10:02gut microbiome. Listen to that summary
10:04again if it didn't click, because that
10:05is the high-level point I need you to
10:07take away.
10:08But now, this is where things get
10:10especially interesting, because not
10:13everyone responds equally to resistant
10:16starch.
10:17So, let's zoom in with greater precision
10:19and address the real question. Why do
10:22some people respond to resistant starch
10:24and others are non-responders? That
10:26brings us to chapter four. Responders
10:29and non-responders. So, to answer this
10:31question, let's turn to our next paper,
10:34published in Cell Metabolism in 2025.
10:36This study was explicitly designed as a
10:39follow-up to understand why roughly 30%
10:41of participants in prior controlled
10:42trials showed limited benefits from
10:44resistant starch.
10:46Now, as the authors note, earlier human
10:48trials consistently found striking
10:50variations in various metabolic health
10:53responses, including liver fat
10:54responses, so we're going to focus on
10:55that. For example, high responders to
10:58resistant starch had a change in liver
11:00fat experienced on the order of 58%,
11:03a 58% reduction in liver fat, that's
11:05huge. Whereas low responders had
11:07reductions as little as 7% as a group.
11:10Same exact protocol, but some people had
11:11a 58% drop and some people only a 7%
11:14drop.
11:15Why? Now, when averaged together, I just
11:17want to point out the effects still look
11:19impressive, but the average obscures the
11:21biology that actually matters. Are you
11:23in the 7% or the 58% group?
11:26Now, importantly, this responder
11:28non-responder pattern has been
11:30replicated across multiple trials.
11:32Similar divergences also occur for BMI,
11:35body fat percent, and insulin resistance
11:37scores. So, put yourself in the position
11:40of participants. You follow the same
11:42protocol. You put in the same effort.
11:45Yet, some people, through no obvious
11:47fault or merit, experience massive
11:49improvements, while others experience
11:51very little return.
11:53So, to make this intuitive and sink in
11:55emotionally, imagine an analogy. Imagine
11:57running hard on a treadmill for 60
11:59minutes. You're staring at a wall. Let's
12:01make it extra boring. Only to discover
12:03that the universe has arbitrarily
12:04decided some people are going to burn
12:072,000 calories from the effort, while
12:08others will burn just 50 calories from
12:10the same effort. It's an imperfect
12:12analogy, but it captures the frustration
12:14and, more importantly, the biochemical
12:17inequity with respect to resistant
12:19starch supplementation. So, the next
12:21question is why? And then, what can we
12:23do about it? So, the investigators went
12:25on to discover that baseline microbiome
12:28composition predicts who will respond to
12:31resistant starch. In particular, there's
12:33one nasty bacterial genus called
12:35Prevotella that is enriched in low
12:37responders and shows a strong inverse
12:40correlation with improvements in liver
12:42fat. This led the researchers to a
12:43hypothesis, one spoiler alert they
12:46ultimately confirmed. The idea is the
12:48presence of this Prevotella bacteria
12:50suppresses the metabolic benefits of
12:51resistant starch. Mechanistically, the
12:54explanation is pretty straightforward.
12:55The Prevotella competes out with other
12:58gut bacteria that can more efficiently
13:00ferment the resistant starch into
13:01beneficial metabolites. So, in simple
13:03terms, more Prevotella, less benefit
13:06from resistant starch.
13:08However, the story doesn't end there,
13:10because gut microbes don't operate in
13:12isolation. They're an ecosystem. They
13:14interact. So, another bacterium, brace
13:16yourself for this name, Bifidobacterium
13:18pseudocatenulatum,
13:20I think you call it. Anyway, let's just
13:22call it BP for short, showed the
13:24opposite pattern. BP is capable of
13:27metabolizing resistant starch and its
13:29presence predicted a stronger metabolic
13:31response, more high responders. So, in
13:33effect, simply put, the responsiveness
13:36of humans to resistant starch depends on
13:37the balance of microbes between things
13:39like prevotella which can't break down
13:41resistant starch and B.P. and other
13:42resistant starch digesters. [music]
13:44So, again, to summarize what we've
13:46learned so far, supplementation with
13:48resistant starch in humans can improve
13:50body weight, fat mass, and visceral fat
13:52and insulin sensitivity and liver fat.
13:54However, not everyone responds equally.
13:57Responsiveness can be predicted by
14:00baseline microbiome composition with
14:02prevotella tending to suppress response
14:04and other microbes known to degrade
14:06resistant starch enhancing
14:07responsiveness. So, if you successfully
14:09followed along, then you've earned
14:11chapter five, actionable insights.
14:14Now, in most of the studies we've
14:15discussed, researchers used type two
14:17resistant starch, specifically high
14:20amylose maize starch. High maize 260 is
14:23what they used specifically. At a dose
14:25of 40 g per day. Now, I know what you're
14:27thinking. 40 g of resistant starch
14:30sounds like a lot and frankly, I was
14:32really surprised to read in the first
14:34study that the investigators reported no
14:36significant gastrointestinal side
14:38effects, no nausea, no bloating, no
14:39diarrhea, or changes in stool frequency.
14:42And between you and me,
14:44I kind of find that hard to believe and
14:45I plan to experiment on myself. Not in a
14:47blinded fashion, but I didn't want to
14:50release those data in this video because
14:52I didn't want my personal anecdote to
14:53bias you whether positive or negative.
14:56So, if you decide to try it, I'd
14:57genuinely be interested to hear what
14:59your experience is with 40 g of type two
15:02resistant starch. That said, there's no
15:04reason to rush. If you choose to try
15:06resistant starch yourself, a cautious
15:08approach would be to titrate up
15:09gradually. Start at 10 g for 1 week, 20
15:13g for 1 week, 30 g for 1 week, and then
15:1540 g thereafter if you're not having any
15:17issues.
15:19As a fast fact, you You also obtain
15:20resistant starch type two from unripe
15:23green bananas if that's your preference.
15:25Now, you need to eat about six of these
15:27green bananas to reach the 40 g dose in
15:29the study. And to be clear, that's not a
15:31challenge. Okay, maybe it's a little bit
15:33of a challenge, but it's also important
15:34to note that resistant starch breaks
15:36down with high heat cooking. So, the
15:38goal is to consume green bananas if you
15:40want to try that raw. Practical options
15:42include eating them as is if you're
15:44super hardcore, or blending them into
15:46drinks like a kefir or a yogurt.
15:49Personally, I think the simplest
15:50approach if you want to try resistant
15:51starch supplementation is a supplement.
15:54High amylose maize starch, the high
15:55maize 260 they used in the study. You
15:57can just take the powder and mix it into
15:59a beverage, something like a kefir to
16:00make some sort of weird probiotic
16:02milkshake, but I'm not here to be a
16:03chef, so I'm very open to your ideas.
16:05And I encourage you to share your ideas
16:07in the comments for the benefit of the
16:08community. Now, I'm sure some of you are
16:10wondering, how do you determine if
16:11you're a responder or a non-responder to
16:13resistant starch? Well, you could get
16:15baseline microbiome testing. I think
16:16some services do assess for the bacteria
16:18we discussed, but it might be more
16:20functional just to follow the metrics
16:21you care about. So, body weight, body
16:24fat if you have a bioimpedance scale or
16:26something like that, and see if you
16:27respond. And remember, about 30% of
16:30people are low responders, meaning 70%
16:33are mid to high responders. So, your
16:34odds of responding are still quite good.
16:37Now, next question. If you're a
16:39non-responder or low responder, even a
16:41mid-responder, can probiotics help?
16:44Possibly. There may be an advantage to
16:46pairing resistant starch with probiotics
16:48that can actually degrade it. One of the
16:50best studied examples is Bifidobacterium
16:53longum, which is known to metabolize
16:55resistant starch including resistant
16:57starch type two, the same type used in
16:59these trials. This is also one of the
17:01key strains in the probiotic I
17:02personally use from Winona Labs, which
17:04was designed not only to function as a
17:06high-quality probiotic which does
17:08degrade resistant starch, but also to
17:10bind microplastics in the gut. Now,
17:12that's a whole separate kettle of fish.
17:14I've written about that more elsewhere.
17:15You can see these articles for more. and
17:17if you want to dive deep into the
17:18microbiome and microplastics, you can
17:21hear my conversation with CEO of Winona
17:23Labs, Dr. Matthew Done, PhD. As always,
17:26there's absolutely no pressure to use
17:28any of the products I use, but if you're
17:30interested, you can use the code stay
17:31curious for 15% off. Never any pressure,
17:34but if I use a product and genuinely
17:36believe in it, I prefer to try to get a
17:38discount code for you and share it for
17:39your consideration. That is it. And this
17:42happens to be my preferred probiotic.
17:43But, wrapping up, resistant starch
17:46represents something really rare in
17:49nutrition science, a simple, accessible
17:51dietary intervention supported by not
17:54one, but multiple rigorous human trials,
17:57mechanistic animal studies, and a clear
17:59biological framework explaining both the
18:01success and failure.
18:04The data make one thing unmistakably
18:06clear. Metabolic health is not just
18:08about what you eat, but how your
18:11personal microbiome interprets it.
18:13The future of nutrition [laughter]
18:15isn't one-size-fits-all prescription.
18:17It's not good or bad. I think that is
18:19awe-inspiring. I think that is humbling.
18:21I think that is exciting. I think that's
18:23why we stay curious. Let me know your
18:25thoughts. I had a really fun time making
18:26this video.
18:38Other resistant starch digester
18:41digesters
18:42resistant starch digesters dige I just
18:45can't say that word. Digesters.

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