This is not medical advice. General information for self-tracking only. If you are under 18, pregnant or breastfeeding, have ever had an eating disorder or a difficult relationship with food, or are managing a medical condition, talk to a doctor or a registered dietitian before you change your calorie intake. If you have diabetes or raised blood sugar, a bowel condition such as IBS or inflammatory bowel disease, or have had bowel surgery, ask them before you change your fibre intake or start a fibre supplement. The figures this site relies on are on the health sources page.

Why fibre keeps turning up in weight loss studies

POUNDS Lost was a Harvard and Pennington trial that put adults with overweight or obesity on calorie-restricted diets, 750 calories a day below their estimated needs, with different splits of fat, protein and carbohydrate. In 2019 a team went back to the 345 participants who had kept food records at the start and at six months, and asked which features of what they actually ate predicted how much weight they lost. On average they lost 7.27 kg.1

The best model they found included fibre, energy density, fat, age, adherence, starting weight, race and several changes in what people ate. Of all of those, the most influential predictor was fibre intake. Fibre was also strongly associated with how closely people stuck to the macronutrient split they had been assigned.1

The authors concluded that fibre "promotes weight loss and dietary adherence". I would put it more carefully than that. This was an analysis of who happened to eat more fibre within a trial, not a test of telling people to eat more of it, and it rests on food records the participants kept themselves. People who eat more beans and vegetables may be the same people who are better at sticking to a diet in general. The model also explained only about 41% of the variation in weight loss, which leaves a lot unaccounted for.1 So it is a reason to take fibre seriously, and not yet proof that fibre did the work.

One goal against thirteen: the fibre-only trial

The direct test came from the University of Massachusetts in 2015. Researchers recruited 240 adults with metabolic syndrome and a BMI of 30 to 40, and randomly assigned them to one of two diets for a year.2

One group got the American Heart Association diet in full: 13 separate goals covering vegetables and fruit, fish, sugar, salt, the shares of carbohydrate, protein and fat, saturated fat and cholesterol, plus an individual calorie target set 500 to 1,000 calories below what they needed to maintain their weight. The other group got a single goal: eat at least 30 g of fibre a day. They were given no calorie target at all.2

After 12 months the fibre group had lost 2.1 kg and the full-diet group 2.7 kg. The difference between them, 0.6 kg, was not statistically significant, with a 95% confidence interval of 0.5 kg in the fibre group's favour to 1.7 kg against it. Dropout was similar, at 9.9% and 12.6%.2

Two things about that result are easy to skip past. The researchers expected the fibre diet to win, and it did not, so the paper is an honest report of a failed hypothesis. And because the trial was designed to show one diet beating the other, the authors say plainly that it cannot prove the two are equivalent. Their own conclusion is that the full diet "may result in up to 1.7 kg more weight loss", and that a fibre-only goal "may be a reasonable alternative" for people who struggle with more complicated plans.2

One more number from the trial deserves to be repeated. Eight people developed diabetes during the year: seven in the fibre group and one in the full-diet group. That difference did not reach statistical significance (p = 0.066), and the paper does not offer an explanation.2 It is still the reason I would not suggest a fibre-only plan, without a calorie target, to anyone who already has raised blood sugar, at least not before a second trial has looked at it.

The group told to eat 30 grams never got there

The part of this trial that matters most for anyone tracking food is in the dietary tables, not the abstract. Intake was measured by unannounced 24-hour recalls over the phone, taken by dietitians who did not know which group each person was in. The fibre group started at 18.8 g a day. Three months in they had added 7.1 g, at six months 6.4 g, and at 12 months 4.7 g.2

That puts them at roughly 23 to 26 g a day, which is my arithmetic from their table. On average the group never reached the one goal it had been given, and the gap widened as the year went on. Attendance was not high either: participants came to about 8 of the 14 sessions on average, in both groups.2

And yet their calorie intake fell by about 200 calories a day over the year, against about 465 in the group that had a calorie target.2 Nobody had asked them to eat less. Aiming at a fibre number seems to have moved what was on the plate enough to cut calories on its own, even though the number itself was missed.

For anyone who tracks food, I think that matters more than the headline result. The goal seems to have changed what people ate even though the group never reached it. It also suggests that 30 g a day is harder than it sounds for someone starting from the usual diet, even with a dietitian and a programme behind them.

Does fibre fill you up? Less often than you would think

The usual explanation for all this is that fibre fills you up, so you eat less. This site has said as much in passing, in the macros guide. The trials that measured it directly are less sure.

A 2011 systematic review from Wageningen University collected randomised trials of fibre and appetite, food intake and body weight, and counted how often a fibre beat its control. Fibres that make a gel in the gut, such as the pectin in fruit, the beta-glucan in oats and barley, and guar gum, reduced appetite in 59% of comparisons. Less viscous fibres did so in 14%. For energy intake measured soon afterwards the figures were 69% and 30%. But the effects on energy intake and body weight were "relatively small", and the authors found no clear dose-response: more fibre did not reliably mean a bigger effect.3

A 2013 review from the University of Minnesota looked only at short studies, a day or less, and was blunter. Across 44 papers and 107 fibre treatments, 39% reduced how hungry people said they felt, and only 22% reduced how much they actually ate. Neither the type of fibre nor the dose predicted the response.4 That last point disagrees with the Wageningen review, which did find that type mattered.

What the trials support, then, is that some fibres, in some foods, take the edge off hunger for some people, while most single doses tested in a lab do not change how much people eat. That is a good deal weaker than "fibre keeps you full".

Fibre supplements, and a result with wide error bars

If fibre from food is hard to raise, a powder looks like a shortcut. A 2017 meta-analysis from the University of Illinois pooled 12 randomised trials, 609 adults with overweight or obesity in all, that gave isolated soluble fibre against a placebo, without asking anyone to cut calories. Over 2 to 17 weeks, the fibre groups lost 2.52 kg more than the placebo groups (95% CI 0.79 to 4.25 kg), and body fat fell by 0.41 percentage points.5

That looks better than the food trials, and the authors are careful about it. They found "considerable" differences between the studies on most outcomes, and say the findings warrant caution for that reason.5 The longest trial was four months. And isolated fibre in a supplement is not what the Institute of Medicine's definition of dietary fibre covers, which is fibre "intrinsic and intact in plants".6 A powder gives you the fibre without the beans or the vegetables it would otherwise have come with, so it may not do what fibre-rich food does.

How much fibre, and per how many calories

The US reference number is an Adequate Intake of 14 g of fibre per 1,000 calories, which works out to 25 g a day for adult women and 38 g for adult men. It was set from research on coronary heart disease, not weight. The average intake in the United States is 17 g a day, and only about 5% of people reach the Adequate Intake.6

The WHO-commissioned meta-analyses in the Lancet in 2019 land in the same place from a different direction. Across 185 prospective studies and 58 clinical trials, the reduction in risk for heart disease, stroke, type 2 diabetes and colorectal cancer was greatest at 25 to 29 g of fibre a day, and the trials showed lower body weight with higher fibre intakes. The authors graded the certainty of the fibre evidence as moderate. They excluded weight-loss trials and supplement trials, so this is about fibre in an ordinary diet.7

There is a wrinkle here for anyone in a deficit. The Adequate Intake scales with calories. MyPlate gives a 35-year-old woman, 165 cm and 75 kg, who exercises moderately, a maintenance estimate of 2,240 calories and a weight-loss target of 1,904. At 14 g per 1,000 calories, that is about 31 g of fibre at maintenance and about 27 g on her target. The fixed figure for women is 25 g either way. I could not find a source that says which one a person eating less on purpose should aim for. In practice the three numbers are close enough that it barely matters, and all of them are well above the 17 g most people eat.6

What the evidence does not settle

Whether fibre causes weight loss, or travels with it. The strongest fibre result in a weight loss trial, from POUNDS Lost, is an analysis of who ate what, not a randomised comparison of fibre.1 The one trial that randomised a fibre goal found it roughly as good as a full diet, not better.2

Who it applies to. The fibre-only trial recruited adults with metabolic syndrome in one Massachusetts city. Most were women, most were white and most had a college education, and the authors themselves say the generalisability is unknown. Nobody followed them after the sessions ended, so we do not know whether the weight stayed off.2

How much of it is fibre and how much is the food. Beans, whole grains, vegetables and fruit come with water, bulk and a lower energy density, and they usually replace something else on the plate. The POUNDS Lost model kept energy density as a separate predictor,1 but no study I found can fully separate the fibre from everything that comes with it. The supplement trials try to, and they disagree among themselves.5

Whether a calorie counter should hit 25 g or 14 g per 1,000 calories, as above. And how quickly to raise it. I looked for a trial on the pace of increasing fibre and did not find one, so I am not going to give you a schedule.

Should your food tracker count fibre?

Here I have to start with my own app. MyPlate does not show fibre. When you scan a meal, the AI estimate that comes back includes a fibre figure, and the app does not display it anywhere. If you want a calorie and nutrient tracker that puts fibre on the main screen, MyPlate is not it today.

I am also less sure than I would like that a fibre number from any app is good. A 2022 study took the 50 foods most often eaten in a Chicago weight-loss study and compared four commercial apps against a research database. CalorieKing and Lose It! agreed closely on everything, fibre included. But fibre was the one nutrient where MyFitnessPal fell short of good agreement, and the worst agreement anywhere in the study was Fitbit's fibre figures for vegetables.9 The rest of that study is in the post on how accurate calorie tracking apps are. A photo is harder still, because fibre is mostly a question of what the food is and how it was processed, and a photo often cannot tell white bread from wholemeal.

The fibre-only trial suggests you do not need precision for it to help. Its participants missed their goal and still changed what they ate.2 So my view is that a food tracker earns its keep here as a rough check, done for a week now and then, not as a second target to hit to the gram every day. Packet labels give you fibre directly. For the rest, knowing roughly whether a day was nearer 15 g or 30 g is enough.

How to use fibre when counting calories to lose weight

Keep calories as the number that decides the weight. The fibre-only group lost a little less than the group with a calorie target, and the difference may have been as large as 1.7 kg over a year.2 If you are already counting calories, fibre is something to add to that, not to replace it with. If counting calories has never stuck for you, a single fibre goal is the one alternative with a randomised trial behind it.

Find out where you start. For one ordinary week, read the fibre on the labels of what you eat most and make a rough estimate for the rest. If you land near the US average of 17 g,6 there is plenty of room.

Swap rather than add. The Academy of Nutrition and Dietetics recommends raising fibre with plant foods while cutting back on foods high in added sugar and fat and low in fibre, and names whole grains, legumes, vegetables, fruits and nuts.6 Adding a bowl of beans on top of an unchanged day adds calories. Swapping white bread for wholemeal, or putting lentils in place of some of the mince, changes the fibre without touching much else. Nuts are worth a note: they are dense in calories, though the body absorbs fewer of an almond's calories than the label says, which I went into in calories you absorb.

Treat supplements as the weaker option. The supplement trials were short and inconsistent,5 and they test a different thing from the food studies. If you want to try one, the medical note at the top applies.

None of this needs a lower calorie target. MyPlate's weight-loss target is 15% below maintenance, and it will not show a target below 1,200 calories a day for women or 1,500 for men, the floor in the NIH/NHLBI guidelines for anyone dieting without medical supervision.8 If adding fibre to the list of things you track is making food feel like a job, or making you anxious, leave it off and talk to someone you trust or a professional.

Common questions

Does fibre help you lose weight?

Probably a little, and the evidence is weaker than it is often made to sound. In a diet trial of 345 adults, fibre intake was the strongest single predictor of weight loss, but that was an analysis of who ate what rather than a test of adding fibre.1 In the one trial that randomised a fibre goal, people lost about as much as on a full calorie-counted diet, not more.2

Can you lose weight by eating more fibre without counting calories?

Some people did, in one trial. Adults with metabolic syndrome told only to eat 30 g of fibre a day lost 2.1 kg in a year, against 2.7 kg for a group on a full diet with a calorie target. They never reached 30 g on average, but their calorie intake still fell by about 200 a day. Seven of them developed diabetes during the year, against one in the other group, a difference that was not statistically significant.2

How much fibre should I eat a day when counting calories to lose weight?

About 25 g a day for women and 38 g for men, which is the US Adequate Intake of 14 g per 1,000 calories.6 The Lancet meta-analyses found the biggest reduction in disease risk at 25 to 29 g a day.7 No source I found says whether to scale the number down when you eat less to lose weight. The average American eats about 17 g, so most people have room to add whichever figure they use.6

Does fibre keep you full?

Sometimes, and less often than people assume. In a review of short studies, only 39% of fibre treatments reduced reported hunger and 22% reduced how much people ate.4 Viscous fibres, such as those in oats, barley and fruit, did better than others in a separate review, but the effects on intake and weight were small.3

Do I need a calorie and nutrient tracker that shows fibre?

No. A week of reading fibre off food labels, with a rough guess for the rest, tells you roughly where you stand, and in the one trial of a fibre goal people benefited without hitting it exactly. MyPlate does not show fibre. In one comparison of four apps against a research database, fibre was MyFitnessPal's one weak spot, so treat any app's fibre number as approximate.9

Count the calories, then check the fibre

Fibre has a better case than most of the things a food tracker could add to its main screen. It predicted weight loss in a large diet trial, a fibre-only goal came close to a full calorie-counted diet in another, and the disease evidence for 25 to 29 g a day is graded moderate. What it does not have is proof that it causes weight loss on its own, or good evidence that it reliably fills you up.

So I would keep the calorie target as the main number, check fibre for a week now and then, and raise it by swapping foods rather than adding them. Most people are a long way below 25 g, and the trial participants who never reached their goal still ate fewer calories for trying.

Sources

Every figure above traces to one of these. If you find a number that doesn't match the source it claims, tell me and I'll correct it.

  1. Miketinas DC, Bray GA, Beyl RA, Ryan DH, Sacks FM, Champagne CM (2019). Fiber intake predicts weight loss and dietary adherence in adults consuming calorie-restricted diets: the POUNDS Lost (Preventing Overweight Using Novel Dietary Strategies) Study. Journal of Nutrition, 149(10):1742-1748. Read on PubMed →
  2. Ma Y, Olendzki BC, Wang J, et al. (2015). Single-component versus multicomponent dietary goals for the metabolic syndrome: a randomized trial. Annals of Internal Medicine, 162(4):248-257. Read on PubMed →
  3. Wanders AJ, van den Borne JJ, de Graaf C, et al. (2011). Effects of dietary fibre on subjective appetite, energy intake and body weight: a systematic review of randomized controlled trials. Obesity Reviews, 12(9):724-739. Read on PubMed →
  4. Clark MJ, Slavin JL (2013). The effect of fiber on satiety and food intake: a systematic review. Journal of the American College of Nutrition, 32(3):200-211. Read on PubMed →
  5. Thompson SV, Hannon BA, An R, Holscher HD (2017). Effects of isolated soluble fiber supplementation on body weight, glycemia, and insulinemia in adults with overweight and obesity: a systematic review and meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition, 106(6):1514-1528. Read on PubMed →
  6. Dahl WJ, Stewart ML (2015). Position of the Academy of Nutrition and Dietetics: health implications of dietary fiber. Journal of the Academy of Nutrition and Dietetics, 115(11):1861-1870. Read on PubMed →
  7. Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L (2019). Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet, 393(10170):434-445. Read on PubMed →
  8. National Heart, Lung, and Blood Institute, NIH (1998). Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. NIH Publication 98-4083. Read the guidelines →
  9. Lin AW, Morgan N, Ward D, et al. (2022). Comparative validity of mostly unprocessed and minimally processed food items differs among popular commercial nutrition apps compared with a research food database. Journal of the Academy of Nutrition and Dietetics, 122(4):825-832. Read on PubMed →

The formulas and limits behind MyPlate's own numbers, with their citations, are on the health sources page.