3 claims that cleared review. Each one shows what has to be true for it to hold and how strongly it is supported — including the places the sources contradict each other.
Formula meal replacement, replacing one to three main meals daily, produces significantly greater weight loss than a standard low-energy diet over 12-52 weeks in adults with type 2 diabetes.
For people with type 2 diabetes, replacing 1-3 meals a day with a formula meal-replacement product tends to produce more weight loss (about 2.4 kg more) than a regular reduced-calorie diet, over 3-12 months.
Only when
replacing 1-3 main meals daily (13-47% of total energy intake) with a formula product
measured over a 12-52 week intervention window
Who
adults with type 2 diabetes
Moderate confidence
Strongest evidence is a high-quality meta-analysis of 9 RCTs (931 participants) with GRADE moderate certainty, the top of the evidence ladder; capped below high because both members trace to a single voice (independent_person_count=1) and the source study itself rates certainty as only moderate.
1 independent person · 2 sources · strongest evidence: meta analysis
Sources
Diets for weight management in adults with type 2 diabetes: an umbrella review of published meta-analyses and systematic review of trials of diets for diabetes remission. · Diabetologia · 2022 · doi:10.1007/s00125-021-05577-2
No measured personal characteristic — such as sex, BMI, age, usual portion size, restrained, emotional or external eating, plate-clearing, food-waste concern, or self-control — consistently affects how much a person's intake decreases when served a smaller portion.
Serving less works about equally well whatever your body type, age or eating style, so there is no profile that needs a different approach. Only the effect on a single meal has been measured.
Only when
tested with alpha corrected to p<.005 for ten hypothesised moderators, pooled N=111 across three randomized trials
one exception survives as a marginal, exploratory signal: BMI may moderate the step from a ~75% to a ~50% portion, significant only in higher-BMI participants and only in sensitivity analyses that did not meet the pre-specified threshold
adults with obesity were 14% of the sample and no underweight adults were enrolled, so the null BMI result is untested at the extremes
socioeconomic position was never examined, and one other study has linked it to portion-size responsiveness
single-meal (or five-day) measurement only; long-term totals were not followed up
Who
adults aged 18-76, BMI 22.5-32.5, no eating-disorder history · Not underweight adults; adults with obesity are under-represented
Moderate confidence
One voice (robinson-e), which people.yaml identifies as the corpus's genuinely independent portion-size voice, behind a pooled analysis of three randomized trials with a pre-registered moderator plan and multiple-comparison correction. Held at moderate rather than high because it is one research group, the sample deliberately excludes the BMI extremes where moderation is most plausible, and every null is a null in a modest sample. All six members concern the same moderation-and-limits proposition, so nothing was excluded.
1 independent person · 1 source · strongest evidence: rct
Sources
Individual differences and moderating participant characteristics in the effect of reducing portion size on meal energy intake: Pooled analysis of three randomized controlled trials. · Appetite · 2021 · doi:10.1016/j.appet.2020.104970
Cutting the portion size of higher-energy items in a shared food environment reduces the energy people buy over and above reducing those items' availability, and the reduction is not made up for by buying more from other categories.
When a canteen made its higher-energy dishes smaller as well as less available, people bought about a tenth less energy — and did not buy more of anything else to compensate.
Only when
the intervention was at least a 10 percent reduction by volume, applied to higher-energy main meals, sides, desserts and bakery items
the combined availability-plus-size intervention cut energy purchased in the targeted categories by 11.5 percent against baseline (95% CI -13.7 to -9.3), and by a further 6.6 percent against the availability change alone (95% CI -7.9 to -5.4)
across all categories combined, including untargeted ones, energy purchased fell 8.6 percent against baseline (95% CI -10.3 to -6.9), so there was no compensatory buying elsewhere
the outcome measured is energy purchased, not energy eaten
the untargeted-category totals contain outliers and erratic time trends that the authors themselves flag
Who
adults eating from a shared or catered food environment; the trial ran across 19 UK worksite cafeterias and 20,327 employees, 96 percent in manual or non-managerial roles · Not individual home eating, which this trial does not test
Moderate confidence
A large, well-powered stepped-wedge randomised trial, but one voice (reynolds-jp; per people.yaml his co-authors hollands-g and kosite-d are recorded as sharing the same voice, so the byline collapses to one). Single-voice support cannot reach high however good the design. Excluded from support: discussion:d2, the authors' dose-response hypothesis, which is marked borderline and which they state was not tested by varying reduction size within the trial.
1 independent person · 1 source · strongest evidence: rct
Sources
Impact of decreasing the proportion of higher energy foods and reducing portion sizes on food purchased in worksite cafeterias: A stepped-wedge randomised controlled trial. · PLOS Medicine · 2021 · doi:10.1371/journal.pmed.1003743
This is a summary of published research, not medical advice. It cannot account for your medications, conditions or history. Talk to a clinician before acting on any of it.