Resistant Starch: Why Cooled Rice and Potatoes Feed Your Gut Bacteria

Somewhere in your feed this month, a cheerful voice has probably promised that yesterday’s rice is a “gut health hack” and that a chilled potato salad can “slash calories.” The videos are everywhere as of early 2025, and they ride on something real: the chemistry of resistant starch, a starch that behaves more like fiber than sugar once it has cooled. They also lean on a 2022 follow-up of a long-running cancer prevention trial that reporters nicknamed “a banana a day.”

The real story is quieter than the headlines but more interesting. A bowl of rice cooked at seven in the evening and eaten cold at noon the next day is, measurably, a different food. Part of it will slip past your own enzymes and arrive, intact, at the bacteria living in your colon.

This article walks through what that means, which claims survive contact with randomised trials, and where a plate of cooled potatoes stops being nutrition and starts being folklore.

What is resistant starch, exactly?

Starch is a chain of glucose molecules that plants pack into grains, tubers and seeds as stored energy. Most of it unravels in your mouth and small intestine, where enzymes clip it into glucose that enters the bloodstream within an hour or two. Resistant starch is the fraction that does not: it resists those enzymes and travels, undigested, to the large intestine. Nutrition scientists class it alongside dietary fiber for that reason, and food labels in many countries count it as fiber.

Researchers sort resistant starch into five types, defined by why the enzymes fail:

• Type 1 is physically locked away, trapped inside intact cell walls in whole grains, seeds and coarsely milled flour.
• Type 2 is raw starch in a tightly packed granule, as in green bananas, raw potatoes and a specially bred high-amylose corn used in supplements.
• Type 3 forms when cooked starch cools and recrystallises, which is the cooled-rice-and-potato story.
• Type 4 is chemically modified starch added to some processed foods.
• Type 5 forms when starch binds to fats during cooking.

The amounts in question are small compared with total carbohydrate. A serving of freshly cooked white rice is mostly digestible starch with well under a gram of resistant starch per 100 grams; cooling raises that to a few grams, not to a bowl of fiber. Estimates from dietary surveys suggest adults in the United States and Europe eat roughly 3–6 grams of resistant starch a day, while people eating traditional diets built on legumes, tubers and whole grains often take in two or three times that. That gap, more than any single “hack,” is what interests gut researchers.

What changed recently

Three threads braided together to push resistant starch into the trending column. The first is social media. Short videos about “day-old rice” and “cooled potato” cycles have been circulating for years, but they surged again in 2024 and early 2025 as creators combined them with the broader fascination with gut bacteria and continuous glucose monitors. Many clips cite a 2015 laboratory experiment, presented at a chemistry conference and never published as a human trial, that estimated large calorie reductions from rice cooked with a little fat and chilled overnight. That estimate came from a test tube, not from people.

The second thread is a genuine trial. In 2022, investigators from the CAPP2 study published a planned long-term follow-up of adults with Lynch syndrome, an inherited condition that sharply raises the risk of bowel and other cancers. Participants had taken either a daily resistant starch supplement or a placebo for an average of two years in the late 1990s and 2000s. Twenty years on, the resistant starch group had about half as many cancers outside the bowel, particularly in the stomach, duodenum and bile ducts, while bowel cancer rates did not differ. News coverage shortened this to “a banana a day,” and the phrase keeps resurfacing.

The third thread is institutional. Over the past two years, consumer health pages at Johns Hopkins and the Cleveland Clinic published or updated plain-language explainers on resistant starch, and the NHS continues to list cooled starchy foods among practical ways to raise fiber intake. When trusted health systems and viral creators are describing the same bowl of rice, search volume follows. The job here is to separate the two accounts.

Why do cooled rice and potatoes contain more resistant starch?

Picture dry rice under a microscope: tight, crystalline granules of starch. Boiling water forces its way inside, the granules swell, and the orderly chains unwind into a soft, gelatinous mass. Food scientists call this gelatinisation, and it is the reason cooked rice is easy to digest. Your amylase enzymes can reach almost every chain.

Cooling reverses part of that process. As the rice drops toward refrigerator temperature over several hours, the straight-chain starch molecules, called amylose, drift back toward one another and lock into new crystals. This is retrogradation, the same chemistry that makes a day-old baguette turn firm. Those fresh crystals are packed too tightly for amylase to bite into, so they pass through the small intestine largely intact. That is type 3 resistant starch.

The numbers are modest but reproducible. A feeding study in healthy adults found that white rice refrigerated for 24 hours and then reheated contained about two and a half times the resistant starch of freshly cooked rice, roughly 1.6 grams per 100 grams versus 0.6, and produced a smaller rise in blood glucose after the meal. Boiled potatoes follow a similar curve: around 1 gram of resistant starch per 100 grams when hot, rising to roughly 3–4 grams after a night in the fridge. Pasta behaves the same way, which is one reason cold pasta salad produces a flatter glucose response than the same pasta served steaming.

Two details matter for the kitchen. Reheating does not undo the gain; the new crystals survive moderate heat, so warmed-over rice keeps most of its resistant starch. And amylose-rich varieties, such as long-grain or basmati rice, retrograde more than sticky, short-grain types, which are higher in the branched starch amylopectin.

How resistant starch feeds your gut bacteria

Whatever escapes your enzymes becomes someone else’s dinner. The colon holds trillions of bacteria, and a subset of them specialise in breaking down starch granules that human digestion left behind. One species, Ruminococcus bromii, is so efficient at cracking open resistant starch that microbiologists describe it as a keystone: it does the heavy lifting, and dozens of other species, including Bifidobacteria and Eubacterium rectale, feed on the fragments it releases.

Fermentation, the process by which bacteria extract energy from carbohydrate without oxygen, produces gases and three short-chain fatty acids: acetate, propionate and butyrate. Butyrate is the one that excites gut researchers. The cells lining the colon draw an estimated 60–70 percent of their energy from it, and in laboratory and animal studies it strengthens the junctions between those cells, calms local inflammatory signalling and lowers the pH of the colon, which discourages some less welcome microbes.

Human feeding trials confirm the first part of this chain reliably. When volunteers add resistant starch for a few weeks, stool butyrate rises and the populations of starch-degrading bacteria expand, usually within days. Those shifts fade just as quickly when the starch is withdrawn, which tells you this is a feeding effect rather than a permanent change.

What the trials cannot yet show is that the extra butyrate translates into fewer diseases. That leap, from a measurable change in stool chemistry to a healthier person years later, is where the evidence thins out, and it is worth keeping the two levels separate whenever you read a confident claim about resistant starch “healing” the gut.

What the evidence actually says: do resistant starches actually work?

The honest answer depends on which outcome you mean, so here is the evidence sorted by strength.

Strong, consistent evidence (multiple randomised trials and meta-analyses): resistant starch lowers the blood glucose rise after a meal when it replaces digestible starch, increases short-chain fatty acid production, and shifts the gut bacterial community toward starch-degrading species. These effects are reproducible across laboratories and populations. They are also surrogate markers, meaning changes in a measurement rather than in how people feel or how long they live.

Moderate evidence (randomised trials with small or mixed effects): pooled analyses of trials in adults with overweight, prediabetes or type 2 diabetes report small average reductions in fasting glucose and fasting insulin, and improved insulin sensitivity, over periods of four to twelve weeks. The gains are real but modest, and results vary with the type and amount of starch used. Effects on LDL cholesterol and inflammatory markers appear in some trials and not others.

Weak or preliminary evidence (single trials, observational data or animal studies): benefits for body weight, appetite, bowel cancer risk in the general population and inflammatory bowel disease fall here. The Lynch syndrome trial is a single randomised study in a high-risk group; it has not been repeated, and it found no change in bowel cancer itself.

Expert opinion only: claims that cooled rice “detoxifies” the gut, repairs a “leaky” intestine in otherwise healthy people, or reverses metabolic disease have no trial support.

So yes, resistant starch does work, in the specific sense that it changes digestion and fermentation in predictable ways. Whether those changes add up to a clinically meaningful benefit for a given person is an open question that the trials have not settled.

Resistant starch benefits for blood sugar: what trials show

Of all the proposed resistant starch benefits, the glucose effect is the one with the clearest mechanism and the most trial data. When part of a meal’s starch is indigestible, less glucose reaches the bloodstream, and what does arrive comes more slowly. In crossover studies where the same volunteers eat hot rice one day and chilled, reheated rice another, the cooled version produces a noticeably lower glucose peak and a smaller total glucose exposure over the following two hours.

Longer trials add a second effect. Several randomised studies lasting a month or more, mostly using high-amylose corn starch supplements in adults with insulin resistance, report improved insulin sensitivity measured by clamp or glucose tolerance tests. The leading explanation is that short-chain fatty acids from fermentation signal to the liver and to gut hormone cells, nudging the body toward handling glucose more efficiently between meals, not just during them.

Three caveats keep this in proportion. First, the trials are small, typically a few dozen participants, and the effect sizes are modest; nobody should expect a cooled potato to replace a diabetes medicine, and nobody taking such a medicine should change it on the strength of a food trend. Second, most trials used purified supplements at amounts well above what a plate of leftovers delivers. Cooling rice is a nudge, not a dose. Third, people with type 2 diabetes respond variably, and some trials in this group found no change in long-term glucose markers.

The practical takeaway is reassuring rather than dramatic: for someone watching glucose, serving starchy sides cooled, or cooked, chilled and reheated, is a reasonable and well-supported habit to layer onto, never instead of, the plan agreed with their clinician.

Does cooled rice have fewer calories? The weight question

This is the claim driving most of the current traffic, and it deserves a precise answer. Resistant starch does yield fewer usable calories than ordinary starch. Digestible starch provides about 4 kilocalories per gram; resistant starch, because bacteria ferment it and keep some of the energy, provides roughly 2. That part is solid.

The arithmetic, however, is humbling. Cooling 100 grams of cooked white rice adds about one gram of resistant starch. That swap saves on the order of 2 kilocalories per 100 grams of rice, perhaps 4–6 kilocalories in a typical serving. The viral figure of a 50–60 percent calorie reduction came from a 2015 laboratory estimate of rice cooked with added coconut oil and chilled; it was presented at a chemistry conference, measured starch digestibility in glassware, and has not been shown in people. Calorie-counting apps that quietly halve the value of “cooled rice” are repeating a projection, not a measurement.

Appetite is a more plausible route to weight effects, and here the evidence is mixed. A handful of short randomised trials found that meals with added resistant starch left participants feeling fuller or eating somewhat less at the next meal; others found no difference. Pooled analyses of longer trials have not shown a consistent change in body weight or waist circumference, and no trial has tested cooled leftovers specifically for weight loss.

Where resistant starch may genuinely help is indirect. People who build meals around lentils, beans, cooled potatoes and whole grains tend to eat more fiber and fewer refined carbohydrates overall, and that pattern is associated with healthier weight in large observational studies. The food matters; the chilling is a bonus, not a magic trick.

The "banana a day" trial: what it did and did not find

Because this study anchors so many headlines, it is worth describing carefully. CAPP2 was a randomised, placebo-controlled trial that enrolled nearly a thousand adults with Lynch syndrome across several countries between 1999 and 2005. Lynch syndrome is an inherited change in DNA repair genes that gives carriers a lifetime bowel cancer risk many times higher than average, along with raised risks of cancers of the womb, stomach, small bowel and bile ducts. Participants were randomised to aspirin or placebo and, separately, to a daily resistant starch powder made from high-amylose corn, or a matching placebo starch, for an average of two years.

The resistant starch arm was designed to test whether feeding the colon’s bacteria could protect the bowel. When first analysed, it showed no effect on bowel cancer or precancerous polyps, and the result was filed as negative. A pre-planned follow-up published in 2022, tracking participants for up to twenty years through cancer registries, changed the picture: the resistant starch group had developed about half as many cancers outside the large bowel, with the clearest difference in the upper gastrointestinal tract. Bowel cancer rates were unchanged.

How to weigh this? It is a single randomised trial, which is a strong design, but the finding was a secondary outcome, the case numbers were small, and the biological explanation, perhaps that short-chain fatty acids alter bile acids or bacterial metabolites reaching the upper gut, remains a hypothesis. The participants also carried a rare genetic condition, so the result cannot simply be transferred to the general population.

What it did not find is as important as what it did. It did not show that bananas, or any food, prevent cancer, and it did not use fruit at all; “a banana a day” was a journalist’s comparison of the amount involved. Anyone with a family history of Lynch syndrome should be discussing surveillance and risk reduction with a specialist, not adjusting breakfast on the basis of a headline.

What food is highest in resistant starch? A comparison table

People searching for resistant starch foods usually expect rice and potatoes at the top of the list. They are not. The richest everyday sources are legumes and unripe bananas, with cooled starchy sides a respectable second tier. Values below are approximate, drawn from published food analyses, and vary with variety, cooking time and how long the food has cooled.

Food (per 100 g as eaten)	Approximate resistant starch	Main type
Green (unripe) banana, raw	4–6 g	Type 2
Cooked white beans or lentils	3–5 g	Types 1 and 3
Boiled potato, cooled overnight	3–4 g	Type 3
Rolled oats, raw (as in overnight oats)	3–4 g	Type 2
Cooked pasta, cooled	1.5–2 g	Type 3
White rice, cooked, cooled and reheated	1.5–2 g	Type 3
Whole-grain bread	1–2 g	Types 1 and 3
Boiled potato, hot	About 1 g	Type 3 (minimal)
White rice, freshly cooked	Under 1 g	Type 3 (minimal)
Ripe yellow banana	Under 1 g	Converted to sugar

A few patterns stand out. Ripening destroys resistant starch: a green banana and a speckled one are nutritionally different fruits, as the starch converts to sugar. Legumes deliver resistant starch along with protein, soluble fiber and minerals, which is why dietitians rank them above any leftover trick. And whole grains contribute less per bite but add up across a day because they appear at every meal.

If the goal is simply more resistant starch, the most efficient single change is a daily portion of beans, lentils or chickpeas. The cooled potato or rice habit is a worthwhile second step, especially for people who already eat those foods and would rather change how they serve them than what they buy.

How to increase resistant starch in your diet without overthinking it

Nobody needs a spreadsheet for this. A handful of kitchen habits raise resistant starch intake steadily and fit into ordinary cooking.

Cook starches ahead. Boil potatoes or rice the evening before, cool them quickly, refrigerate, and use them the next day in salads, fried rice, hash or soup. Reheating is fine; most of the resistant starch survives. Pasta salad, cold sushi rice and potato salad are all accidental resistant starch dishes that people have enjoyed for generations.

Choose varieties wisely. Long-grain and parboiled rice retrograde more than sticky short-grain rice. Waxy potatoes hold together in salads and cool well. Al dente pasta is less fully gelatinised than soft pasta and keeps more of its structure.

Lean on legumes. Canned chickpeas, lentils and beans are already cooked and cooled, which means they arrive with their resistant starch intact. Half a cup in a salad or stew most days is the single biggest lever available.

Eat some oats raw. Overnight oats soaked in milk or yogurt keep the raw-granule resistant starch that porridge cooks away.

Pick the greener banana. A firm, slightly green banana sliced into cereal delivers several grams; a soft, spotted one delivers almost none.

Go gradually. Fermentation produces gas, and a sudden jump from a low-fiber diet to beans at every meal is a recipe for bloating. Adding one new source a week gives the gut bacteria time to adjust, and most people find the early flatulence settles within a couple of weeks.

Supplements made from green banana flour, raw potato starch or high-amylose corn are sold as foods, and the trials that showed glucose effects mostly used these products. They are an option for people who want precision, but they lack the protein, minerals and other fiber that come packaged with whole foods, and they are easy to overdo.

Cooled rice resistant starch and food safety: reheat with care

Every conversation about cooled rice resistant starch should include a word about Bacillus cereus. This soil bacterium forms heat-resistant spores that survive cooking. If cooked rice sits at room temperature, the spores germinate and the bacteria multiply, producing a toxin that is not destroyed by reheating. The result, sometimes called “fried rice syndrome,” is a short but unpleasant bout of vomiting or diarrhea that begins within one to sixteen hours of eating.

The NHS sets out simple safeguards that fit the resistant starch habit neatly:

• Serve rice as soon as it is cooked, or cool it quickly, ideally within an hour, by spreading it on a tray or dividing it into shallow containers.
• Refrigerate cooled rice promptly and eat it within 24 hours.
• Reheat until steaming hot throughout, and never reheat the same batch more than once.
• Do not leave cooked rice, potatoes or pasta out overnight on the counter, however tempting the “let it cool naturally” advice sounds online.

Potatoes and pasta carry a similar, if smaller, risk, and the same rules apply. Cooked potatoes stored in airtight containers at room temperature have been linked to rare outbreaks of botulism, a serious illness, which is another reason refrigeration is non-negotiable.

None of this undermines the nutrition. Retrogradation happens in the refrigerator just as well as on the counter; it simply takes a few more hours. Rapid cooling followed by overnight chilling delivers the resistant starch gain and keeps the bacteria that matter in your colon rather than on your plate.

People who are pregnant, older, very young or living with weakened immunity are more vulnerable to foodborne illness and have the most to gain from following these steps exactly.

Who should not eat resistant starch?

For most people resistant starch is simply a component of ordinary food, and there is no evidence that eating cooled rice or a bowl of lentils is harmful. A few groups, though, should approach it thoughtfully.

People with irritable bowel syndrome. Fermentation produces gas, and in a sensitive gut that gas can mean pain, bloating and unpredictable bowel habits. Resistant starch is not formally one of the FODMAPs, the short-chain fermentable sugars restricted in a common IBS diet, but legumes are high in FODMAPs for other reasons, and some people with IBS report that even cooled potatoes trigger symptoms. Trials of resistant starch in IBS are small and inconsistent. A gradual introduction, one food at a time, lets a person learn their own threshold.

People with small intestinal bacterial overgrowth or active inflammatory bowel disease. If bacteria have colonised the small intestine, or the bowel lining is inflamed, extra fermentable carbohydrate may worsen symptoms. Studies in these conditions are preliminary, and dietary changes should be planned with the treating gastroenterologist or dietitian.

People on a low-fiber diet for medical reasons. Before colonoscopy, after certain bowel surgeries, or during a flare of diverticulitis, clinicians sometimes advise limiting fiber. Resistant starch counts, and the medical instruction takes precedence over any wellness goal.

People who manage blood glucose with insulin or glucose-lowering medicines. Cooled starches are not dangerous, but because they blunt the glucose rise, a large and sudden shift in how meals are prepared could change how a dose behaves. Anyone in this situation should mention the change to their diabetes team rather than adjust medicines themselves.

For everyone else, the main “side effect” is wind, and the main risk is the food-safety one described above.

Common myths about resistant starch, corrected

Myth: cooled rice has half the calories. The measured gain in resistant starch from cooling white rice is about one gram per 100 grams, worth a few kilocalories per serving. The 50–60 percent figure is a projection from a laboratory experiment that has not been confirmed in people.

Myth: reheating destroys the benefit. Retrograded starch crystals are heat-stable at normal reheating temperatures. Feeding studies that reheated cooled rice still found higher resistant starch and lower glucose responses than freshly cooked rice.

Myth: letting rice cool slowly at room temperature makes more resistant starch. Retrogradation happens in the fridge too; it just needs a few more hours. Slow counter cooling adds no meaningful benefit and raises the risk of Bacillus cereus food poisoning.

Myth: a banana a day prevents cancer. The trial behind that phrase used a purified corn starch supplement in people with an inherited cancer syndrome. It found fewer cancers outside the bowel and no change in bowel cancer, and it has not been repeated. Fruit was never tested.

Myth: resistant starch “heals leaky gut” in healthy people. Butyrate supports the colon lining in laboratory models, but “leaky gut” is not an established diagnosis in otherwise healthy adults, and no trial has shown resistant starch repairs intestinal permeability in that population.

Myth: more is always better. Several studies found that the highest intakes produced the most bloating without extra metabolic benefit. The gut bacteria that break down resistant starch need time to expand, and intake above what a varied diet of legumes, whole grains and cooled starches provides has not shown added value.

Myth: potato starch stirred into water is the same as eating potatoes. Raw potato starch is almost pure type 2 resistant starch, with none of the potassium, vitamin C or protein of the vegetable. It is a supplement, and supplement rules about moderation apply.

When to see a doctor

Resistant starch is a food component, not a treatment, and adding cooled potatoes or a daily portion of lentils rarely calls for medical input. Some situations do.

Seek prompt medical care if, after eating stored rice or other leftovers, you develop repeated vomiting, diarrhea that lasts more than two days, signs of dehydration such as dizziness or very little urine, a high fever, or blood in the stool. Symptoms of botulism, including blurred or double vision, drooping eyelids, difficulty swallowing or speaking, and muscle weakness that spreads downward, are a medical emergency.

Book an appointment, rather than adjusting your diet alone, if you notice:

• bloating, abdominal pain or a change in bowel habit that persists for more than a few weeks, especially if it is new after age 50;
• unintended weight loss, persistent tiredness, or iron deficiency alongside gut symptoms;
• blood in or on the stool, or black, tarry stools, at any age;
• a family history of bowel cancer, Lynch syndrome or other inherited cancer syndromes, which should prompt a conversation about screening age and genetic assessment, not a change in starch intake;
• any plan to use resistant starch, or a cooled-starch eating pattern, to manage diabetes, prediabetes or weight while taking prescribed medicines.

People with diabetes should never reduce or stop a glucose-lowering medicine because a food trend promises to “replace” it. Changes in meal composition can change how medicines act, and the dosing decision belongs to the prescribing clinician. Likewise, anyone with IBS, inflammatory bowel disease or a history of bowel surgery who wants to raise fermentable fiber should discuss the plan with their gastroenterologist or a registered dietitian first.

Finally, if the online advice you are reading tells you to buy a specific powder, follow a strict daily amount, or ignore food-safety guidance in pursuit of “maximum resistant starch,” treat that as a reason to check with a professional rather than a reason to comply.

Frequently asked questions

What food is the highest in resistant starch?

Green, unripe bananas and cooked legumes such as white beans, lentils and chickpeas top the everyday list, at roughly 3–6 grams per 100 grams. Cooled boiled potatoes come next at around 3–4 grams, followed by raw oats, then cooled pasta and cooled rice at about 1.5–2 grams. Raw potato starch and high-amylose corn starch supplements contain far more by weight but lack the nutrients of whole foods.

How do I increase resistant starch in my diet?

Cook potatoes, rice and pasta ahead, cool them quickly, refrigerate overnight and eat them cold or reheated the next day. Add a daily portion of beans, lentils or chickpeas, choose slightly green bananas, and try overnight oats instead of porridge. Introduce one new source a week so gut bacteria adjust and bloating stays manageable.

Who should not eat resistant starch?

Almost everyone can eat it, but people with irritable bowel syndrome, small intestinal bacterial overgrowth or active inflammatory bowel disease may find fermentable starch worsens gas and pain and should go slowly or seek dietitian advice. Anyone told to follow a low-fiber diet before a procedure or after bowel surgery should follow that instruction. People using insulin or glucose-lowering medicines should tell their diabetes team before changing how they prepare starches.

Do resistant starches actually work?

Yes, for the outcomes that have been tested well: randomised trials consistently show lower blood glucose after meals, more short-chain fatty acids such as butyrate, and growth of starch-degrading gut bacteria. Evidence for weight loss is weak and inconsistent, and evidence for cancer prevention rests on one trial in a high-risk genetic group. Resistant starch changes digestion measurably; whether that improves long-term health for a given person is not yet proven.

Does reheating cooled rice destroy the resistant starch?

No. The starch crystals that form during cooling are stable at normal reheating temperatures, and feeding studies that reheated refrigerated rice still measured higher resistant starch and a lower glucose response than freshly cooked rice. Reheat until steaming hot throughout for food safety, and reheat a batch only once.

How long does rice need to cool to form resistant starch?

Most of the measurable gain appears after about 12–24 hours in the refrigerator, which is why studies typically test rice chilled overnight. Longer storage adds little. Cool the rice quickly first, within an hour of cooking, then refrigerate; slow cooling on the counter does not create more resistant starch and allows Bacillus cereus bacteria to multiply.

Is cooled rice resistant starch a type of fiber?

Functionally, yes. Resistant starch is counted as dietary fiber by most nutrition authorities because it passes through the small intestine undigested and is fermented in the colon, like soluble fiber. It differs chemically from the fiber in bran or vegetables, but it contributes to daily fiber intake and to the short-chain fatty acids that feed the cells lining the colon.

What are the main resistant starch benefits shown in trials?

The best-supported benefits are a smaller rise in blood glucose after meals, improved insulin sensitivity in adults with insulin resistance over several weeks, and higher production of butyrate, which nourishes colon cells. Some trials show small reductions in LDL cholesterol or inflammatory markers; others do not. Benefits for weight, appetite and disease prevention remain unproven.

Does cooled pasta have resistant starch like rice and potatoes?

It does. Cooked pasta that has been refrigerated contains roughly 1.5–2 grams of resistant starch per 100 grams, more than freshly cooked pasta, and produces a flatter blood glucose curve in crossover studies. Cooking it al dente preserves more structure, and reheating keeps most of the gain, so leftover pasta reheated the next day behaves similarly to pasta salad.

Can resistant starch help with weight loss?

The evidence is weak. Resistant starch supplies fewer usable calories than digestible starch, but cooling a serving of rice saves only a few kilocalories, and pooled randomised trials have not shown a consistent change in body weight. A few short studies found modest increases in fullness. Any weight benefit most likely comes from eating more legumes, whole grains and fiber overall rather than from chilling leftovers.

References

• MedlinePlus: Fiber
• NHS: How to get more fibre into your diet
• NHS: Can reheating rice cause food poisoning?

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.