Retail's GLP-1 Forecast Assumes the Weight Stays Off. The Evidence Still Doesn't Agree.

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Extended sizes for women's apparel on Target's website fell 37 percent between March 2025 and March 2026, and Old Navy's fell 12 percent over the same span, according to tracking data compiled by the retail intelligence firm EDITED. This outlet reported those figures on August 17, in "Target's Plus-Size Selection Fell 37 Percent in a Year, as Old Navy's Slid Too." Neither company said why. What sits underneath that coverage, and underneath a good deal of the industry's planning since, is a forecast: that GLP-1 drugs are moving a durable share of apparel demand out of larger sizes and into smaller ones. That forecast now carries a dollar figure, a software vendor's name, and a clinical assumption at its center that the medical literature has spent this year arguing about.

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The most-quoted number in retail's GLP-1 forecast originates with Impact Analytics, a company that sells AI retail planning, merchandising, and inventory software. Its study, announced September 29, 2025 and expanded in a follow-up released June 5, 2026, models aggregated point-of-sale and returns data from major US apparel retailers and concludes that more than 400 million apparel units could be misaligned with demand by 2027, putting more than $5 billion in inventory value and margin at risk. The company's public write-up of that analysis does not publish sample sizes or model detail, and does not address discontinuation or weight regain — it treats the shift toward smaller sizes as directionally persistent. From there the figures traveled. Ali Furman, PwC's consumer markets industry leader, restated both on The Robin Report's Retail Unwrapped podcast on April 10, 2026 without naming their origin, alongside PwC's own estimate that 20 percent of US households had at least one GLP-1 user as of December 2025, up from 9 percent a year earlier. Bold Metrics, a San Francisco body-data firm that sells sizing software to apparel retailers, repackaged the same numbers in an April 17, 2026 analysis aimed squarely at merchandisers deciding what to buy. On the same podcast, Liza Amlani, founder of the Retail Strategy Group, cautioned against over-correcting, describing a "rebound exposure gap" and putting the share of weight that returns within a year of stopping at 60 to 70 percent.

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Amlani's figure is a fair reading of the trial literature. The STEP 1 extension, published in Diabetes, Obesity and Metabolism in 2022, followed a 327-participant subset for a year after semaglutide and the trial's lifestyle support were both withdrawn: mean weight loss at week 68 was 17.3 percent, participants regained 11.6 percentage points over the following year, and finished 5.6 percent below where they started — two-thirds of the loss handed back. A post hoc analysis of Eli Lilly's SURMOUNT-4 trial, summarized by the American College of Cardiology in December 2025, took the 670 participants who had lost at least 10 percent on tirzepatide; of the 308 moved to placebo, 254 — 82.5 percent — regained more than a quarter of what they had lost by week 88, with waist circumference, blood pressure, and A1c drifting back in step. A systematic review and nonlinear meta-regression of six randomized trials covering 3,236 participants, published in eClinicalMedicine on March 4, 2026 by researchers at the University of Cambridge, put regain at 60 percent of lost weight one year after cessation, leveling off at an estimated 75.3 percent.

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The real-world data reads differently, and part of the reason is that it is not asking the same question. A study of 4,182 patients on the federated health-record platform run by the analytics company nference — posted to medRxiv in January and published in Oxford's Biology Methods and Protocols on April 20, 2026 — found roughly two-thirds of patients held steady or kept losing in the six months after their last semaglutide or tirzepatide prescription, with 33.0 percent of semaglutide patients and 27.6 percent of tirzepatide patients regaining. Epic Research reached a similar shape two years earlier and independently: across 20,274 semaglutide patients in the Cosmos data set, 56.2 percent were at or below their stopping weight a year later. But the trials measure how much of the lost weight came back, and the real-world studies measure whether a given patient's weight went up at all. The trials run a year; the nference study's headline window is six months. And a last filled prescription is not the same event as stopping the drug — the authors say so themselves, noting that patients may have carried on through a medical spa, a telehealth provider, or a compounding pharmacy, none of which their data would see.

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Destination XL is a big-and-tall menswear chain rather than a women's plus-size retailer, but it is the company that has looked hardest at this question and said so on the record — and it has separately told investors that as many as 25 percent of its customers may now be on GLP-1 drugs. Its chief executive's position is that the research the company commissioned and bought does not show the correlation, and that the company reads the impact as larger than it expected anyway. Meanwhile the company that calls itself the largest direct-to-consumer brand of women's plus-size apparel in North America shed more than a quarter of its stores without invoking the drugs at all: Torrid went from roughly 632 locations in June 2025 to 463 by the first quarter of 2026, on net sales down 7.6 percent, and the reason it gave investors was cutting fixed costs and shifting to digital, which it said already accounted for nearly 70 percent of demand. GLP-1s appear nowhere in its earnings calls. The next read on any of this arrives almost immediately — Target reports second-quarter results on August 19, 2026, and Gap Inc. on August 27.