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Legumes and weight loss: what fullness can and cannot tell us

緑と赤のレンズ豆を使ったスープが一つの器に盛り付けられている 立川駅徒歩1分年中無休の溶岩ホットヨガスタジオ

Replacing rice or meat differs from adding beans

A randomized controlled trial in Korea involved 400 participants with obesity. The legume-enriched diet group replaced one-third of their refined rice with legumes at each meal, three times per day. After 12 weeks, average weight loss was 2.87 kg in that group and 0.17 kg in the usual-diet group. The difference between groups was significant.[14] The authors did not report a confidence interval for that weight difference in the abstract.[14]

This result needs to be read as a specific change to an existing diet. Participants did not simply finish their usual meals and then add a bean snack. Nor did the intervention remove all rice. It changed part of a staple food. The participants were Korean people with obesity, so their starting body size and dietary context are also part of the result.[14]

Another trial replaced part of the meat in the diet. It followed 102 healthy working-age men, with a mean age of 38 years, for 6 weeks. The comparison group ate 760 g of red and processed meat per week. The legume group ate 200 g per week and received non-soy legume foods supplying protein equivalent to the meat that had been removed.[18] Protein content, rather than equal food weight, was the basis for that exchange.

At the end, the legume group had significantly lower weight and BMI than the comparison group.[18] The abstract reports that a difference occurred, but does not give its size in kilograms or a confidence interval. Those missing details matter when asking whether the change would be noticeable in everyday life. A weight-loss amount from the rice trial cannot be borrowed to fill this gap: the foods, participants, and intervention were different.

The nutritional results also deserve space. The legume group had higher intakes of fiber and some other nutrients, but lower vitamin B12 intake and status, and lower iodine status, than the comparison group. The authors judged iodine, iron, and vitamin B12 adequacy to have been maintained in the short term.[18] A lower value relative to another group is distinct from a diagnosis of deficiency. Both the differences and the authors’ adequacy assessment apply to this partial substitution over 6 weeks.

At home, a stew combining beans with less meat can make the idea of substitution concrete. So can a meal that replaces part of its rice with legumes. These are illustrations of how to make a change visible, rather than claims that a particular household recipe reproduces the trial meals. The meat study retained some meat and included only men.[18] It cannot establish that every family member should make the same dietary change.

A further trial helps distinguish energy restriction from an additional legume effect. It included 127 Chinese participants with prediabetes living in Singapore, with a mean age of 62.2 years. Over 16 weeks, both groups followed calorie-restricted diets; the intervention group followed a legume-enriched diet with multiple components. BMI fell in both groups, with minimal difference between them.[20]

Some blood-glucose and lipid measures improved more in the intervention group. That should not be rewritten as substantially greater weight loss caused by beans.[20] A diet’s value can extend beyond weight, but an article discussing weight needs to use the weight result. Because several dietary components changed together, the findings also cannot be attributed to legumes alone.

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Soy findings depend on who and what were compared

Soy requires its own reading. A 2017 meta-analysis examined 24 soy trials and 17 isoflavone trials. Overall, soy did not have a statistically significant effect on body weight, waist circumference, or fat mass.[12] Isoflavones are components found in soy; studies of those components were distinguished from studies of soy itself. Grouping every soy-related intervention under a single food label would conceal that difference.

Within the same analysis, the subgroup of participants with obesity showed a weight difference of +0.80 kg, with a 95% confidence interval of 0.15 to 1.45 kg.[12] The overall absence of a significant effect and an increase in a particular subgroup can both be reported. They describe different levels of the analysis.

When soy was compared with meat, the difference was also on the increase side: +0.36 kg, with a 95% confidence interval of 0.09 to 0.64 kg, a significant result.[12] These are pooled differences relative to comparison diets. They should be distinguished from an individual participant’s change from baseline. They also show why the identity of the comparison food belongs beside the result.

Conditions involving at least 40 g of soy protein per day showed a significant weight difference of +0.94 kg, with a 95% confidence interval of 0.11 to 1.77 kg. Short interventions lasting 1–3 months showed +0.45 kg, with a 95% confidence interval of 0.05 to 0.86 kg.[12] The idea that a larger soy intake must favor weight loss does not fit these findings. The intake category concerns soy protein, rather than the total weight of a soy food.

A separate 2019 meta-analysis included 22 trials and 870 participants with overweight or obesity. It reported significant weight reductions of −0.37 kg in Asian participants and −0.59 kg in premenopausal women.[15] These are results for particular groups, not a uniform effect demonstrated in every participant. The abstract does not provide confidence intervals for those weight differences.[15]

Readers may recognize themselves in a subgroup description. Sharing part of that description still leaves questions about the intervention and comparison diet. A subgroup estimate describes an average under the conditions studied; it does not forecast weight loss from the number of tofu packages an individual buys. The information about participants and dietary changes is too limited for that conversion.[12][15]

The disagreement is best read by comparing the analyses’ scope: their included trials, participants, forms of soy, and comparison foods. The evidence presented here includes an analysis with no significant overall effect, increases under certain conditions, and small reductions in specified populations.[12][15]

Neither abstract presents a matched-amount comparison of tofu, natto, and soy milk. These results do not establish a weight-loss ranking for those foods. Choosing foods for a menu and claiming that a particular form causes weight loss are separate decisions.[12][15]

Finally, grams of soy protein are not grams of tofu or a count of natto packages. Converting a component dose into a food quantity requires additional information. Where the form and amount tested are unclear, leaving the uncertainty visible is more accurate than forcing a research number onto a household serving.

立川駅徒歩1分年中無休の溶岩ホットヨガスタジオ

Common misconceptions

“If bean eaters weigh less, beans must be the cause.” An observational study of 15,185 US adults found that higher legume intake was associated with lower weight change over the previous 10 years and lower current measures of body size. After fiber intake was also included in the statistical analysis, those associations were no longer significant.[9] This was an analysis of previous weight change, rather than a trial assigning everyone beans and following their weight for 10 years.

Accounting for fiber changed the apparent relationship between legumes and body size. Legume intake overlaps with characteristics of a fiber-containing diet, making the influence of beans alone difficult to isolate.[9] Replacing the word “association” with “effect” would assign the background of someone’s diet to a single ingredient. The observational result cannot do that work.

“Fullness rose by 31%, so food intake fell by 31%.” The percentage refers to a post-meal fullness measure. Intake at the next meal did not differ significantly.[3] Percentages cannot be carried from one outcome to another just because both concern eating. You can acknowledge feeling satisfied while keeping expectations about weight grounded in studies that measured food intake and weight directly.[2][3]

“More beans mean more weight loss for as long as I keep eating them.” The median intervention in the representative weight meta-analysis lasted 6 weeks, and the authors said long-term sustainability needed investigation.[2] A 2010 review mainly supported weight loss when pulse intake accompanied energy restriction. The later meta-analysis reported a small difference even in diets not intended to restrict calories.[2][4] The evidence developed, but it did not establish an optimal dose or a guaranteed long-term outcome.

The evidence does not support placing a short-term average difference on a monthly calendar and extending it in a straight line through the end of the year. Beans can be a candidate ingredient in meals you keep making, but they are not a subscription to a fixed rate of weight loss.[2] Preferences, meal preparation, and what they replace still matter when deciding how to use the research in daily life.

What you can do today

  • If rice is a regular staple, consider trying a meal that replaces one-third of the refined rice with legumes. The Korean trial made that substitution at each meal, three times daily, for 12 weeks; its result belongs to participants with obesity under those conditions.[14]
  • When making a meat stew, consider replacing some meat with non-soy legumes. The trial reduced red and processed meat from 760 g to 200 g per week and supplied the protein equivalent of the removed 560 g through legume foods, rather than exchanging equal food weights. It studied only men for 6 weeks; vitamin B12 and iodine status were lower in the legume group, although the authors judged short-term nutritional adequacy to have been maintained.[18]
  • In a lunchbox, use beans in place of part of the usual staple instead of keeping the rice and other dishes unchanged and adding another dish. The rice trial replaced one-third of refined rice; it tested substitution, rather than an extra bean serving on top of the usual meal.[14]
  • Weigh the beans used and record the portion eaten and how long you continue. The weight meta-analysis had a median intake of 132 g per day and duration of 6 weeks. In the same notes, distinguish satisfaction after the bean meal from how much you eat at the next meal: the fullness analysis found a difference in the former but no significant difference in the latter.[2][3]
  • Before using a soy finding to plan meals, check whether the comparison was meat and which participant group showed the result. Read both increases and decreases together with their conditions.[12][15]

The rice substitution describes the intervention studied in Korean participants with obesity. Trying the idea at home does not promise the same weight loss.[14] The practical aim is to make your dietary change clear enough to understand, rather than treating a trial’s average as a household target.

yogaのレッスン前の様子生徒の足もとにあるヨガマット 立川駅徒歩1分年中無休の溶岩ホットヨガスタジオ

Pair meal substitutions with a weekly routine at On the Shore Tachikawa

Changing part of a meal to beans is one habit to keep; making room in the week for movement is another. On the Shore Tachikawa provides a place to maintain the movement habit alongside those meal substitutions.

For a first visit, the yoga trial includes a 60-minute lesson and rentals of a mat, 2 bath towels and 1 face towel for ¥1,980 including tax. The prices page and trial booking page provide the next steps.

The lava-stone hot yoga studio is on the third floor of Etoile Bldg at 2-14-10 Akebonocho, Tachikawa, Tokyo, just a 1-minute walk from JR Tachikawa Station’s North Exit. With more than 25 kinds of yoga lessons, it also offers room-temperature yoga, Pilates, women-only kickboxercise, boxercise, HIIT and personal training, as listed on the studio website. Many of our yoga instructors speak English, and the studio’s owner often helps guests from the US bases in English herself.

To fit movement around everyday meals and other commitments, the studio is open every day 8:00–23:30. Participation requires checking the health conditions: guests instructed by a doctor to avoid exercise cannot take part. Pregnant guests must choose room-temperature maternity yoga rather than joining a lava-stone hot yoga lesson.

References

  1. Effects of Non‐Soy Legumes on Body Weight and Body Composition: A Systematic Review and Meta‐Analysis of Randomized Controlled Trials — Reza Rahmanian et al., 2026, Food Science & Nutrition. DOI: 10.1002/fsn3.71365
  2. Effects of dietary pulse consumption on body weight: a systematic review and meta-analysis of randomized controlled trials. — Shana J. Kim et al., 2016, The American journal of clinical nutrition. DOI: 10.3945/ajcn.115.124677
  3. Dietary pulses, satiety and food intake: A systematic review and meta‐analysis of acute feeding trials — Siying S. Li et al., 2014, Obesity. DOI: 10.1002/oby.20782
  4. Pulse consumption, satiety, and weight management. — M. McCrory et al., 2010, Advances in nutrition. DOI: 10.3945/an.110.1006
  5. Legume Intake, Body Weight, and Abdominal Adiposity: 10-Year Weight Change and Cross-Sectional Results in 15,185 U.S. Adults — L. Tucker, 2023, Nutrients. DOI: 10.3390/nu15020460
  6. Effect of Soy and Soy Isoflavones on Obesity-Related Anthropometric Measures: A Systematic Review and Meta-analysis of Randomized Controlled Clinical Trials. — M. Akhlaghi et al., 2017, Advances in nutrition. DOI: 10.3945/an.117.015370
  7. Adiponectin and 8-epi-PGF2α as intermediate influencing factors in weight reduction after legume consumption: a 12-week randomised controlled trial — Youngmin Han et al., 2020, The British Journal of Nutrition. DOI: 10.1017/s0007114521000970
  8. Soy Products Ameliorate Obesity-Related Anthropometric Indicators in Overweight or Obese Asian and Non-Menopausal Women: A Meta-Analysis of Randomized Controlled Trials — Yuze Mu et al., 2019, Nutrients. DOI: 10.3390/nu11112790
  9. Beans Improve Satiety to an Effect that Is Not Significantly Different from Beef in Older Adults: A Randomized, Crossover Trial — Megan J. Fluit et al., 2025, The Journal of Nutrition. DOI: 10.1016/j.tjnut.2025.02.008
  10. Nutritional and health benefits of a partial substitution of red and processed meat with non-soy legumes: a 6-week randomized controlled trial in healthy working-age men — Sari Bäck et al., 2025, European Journal of Nutrition. DOI: 10.1007/s00394-025-03783-x
  11. A legume-enriched diet improves metabolic health in prediabetes mediated through gut microbiome: a randomized controlled trial — Xiaorong Wu et al., 2025, Nature Communications. DOI: 10.1038/s41467-025-56084-6

Cover photo: A bowl of soup made with green and red lentils. (Photo: Whoisjohngalt / CC BY-SA 4.0 / Wikimedia Commons)

Information as of October 2026. For your own health, consult a doctor.

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