How GLP-1 Adoption Changes BFCM Inventory Planning

You can order the right amount of inventory for Black Friday and Cyber Monday (BFCM) and still get the buy wrong. If customers suddenly want different sizes, formulations, or products than they did last year, your total unit count won’t save you.

For apparel and health and wellness brands heading into BFCM, that creates a new inventory planning challenge: demand may be growing, but not necessarily in the same SKUs, sizes, or categories that won last year.

The rise in GLP-1 use is one driver of this. 

According to Gallup, the percentage of U.S. adults who currently take GLP-1 medications for weight loss purposes has risen to 11% in 2026, up significantly from 3% in 2024. Furthermore, PwC found that 73% of current GLP-1 users reported a meaningful change in clothing size, while apparel spending increased 9.9% six to eight months after starting treatment. 

Consumer behavior is moving faster than traditional seasonal buying cycles. The brands that win won’t necessarily be the ones that make the biggest inventory bet. They’ll be the ones that can adjust fastest as the signal gets clearer.

Your BFCM Forecast Could Be Right and Your Inventory Still Wrong

For apparel brands, changing body sizes can change the size curve long before last year’s sales data catches up. That means an apparel brand could have enough units for BFCM and still stock out of the sizes customers suddenly want while slower sizes pile up.

Wellness brands face a similar assortment problem. BCG found active GLP-1 users expect to spend 20% more on protein and fiber supplements, collagen, hydration products, and hair and skin supplements.

The opportunity here is real, but so is the risk of chasing it too aggressively.

And this matters far beyond GLP-1s. Our Ecommerce Growth, Explained 2026 report found that 93% of ecommerce operators changed their inventory strategy in the past year, but there was no single direction of travel. 39% increased safety stock, 38% concentrated investment in proven products, 35% held less inventory and relied on faster replenishment, and 34% ordered smaller quantities more frequently.

The lesson: there is no perfect inventory strategy. There is only a strategy with enough room to adjust.

Build a BFCM Inventory Plan That Can Change Its Mind

While it’s nearly impossible to fully eliminate uncertainty before BFCM, you can build a plan that can absorb it.

That means making more deliberate bets upfront, watching the signals that tell you when demand is shifting, and keeping enough inventory and capital flexibility to respond without throwing the rest of the season off course. The smartest plan gives you room to go deeper when you’re right—and room to change course when you’re not. Here are three ways to achieve this:

1. Treat every SKU like an investment

For BFCM, start by separating conviction from speculation. Proven hero products may justify deeper buys and greater safety stock, while emerging GLP-1-adjacent categories or changing apparel size curves may warrant smaller initial commitments until demand becomes clearer.

Historical sales also still matter. Use data from previous seasons to identify patterns, benchmark performance, and improve demand forecasts. When consumer behavior itself is changing, historical data provides a starting point for planning where you’re willing to go deep, where you want optionality, and which products you can replenish quickly if they outperform.

2. Put returns into the demand forecast

ReturnPro reports that GLP-1 users are buying multiple sizes as they navigate fit changes and inconsistent brand sizing. Some are also holding purchases longer before deciding what to return, adding more variability to when inventory actually comes back into circulation.

That can distort your BFCM demand signals since a spike in orders for several adjacent sizes doesn’t necessarily mean all of those units will stay sold.

Brands should monitor return reasons by SKU and size, improve measurements and fit guidance, and model expected returns into inventory availability and cash forecasts. 

3. Fund the Reorder, Not Just the Forecast

Demand forecasting tells you what you think will happen, but your capital plan determines what you can do when it doesn’t. That distinction matters heading into BFCM because inventory, freight, suppliers, and marketing often require cash long before peak season revenue lands. 

We found that forecasting demand accurately and managing the gap between supplier payments and incoming revenue are now among ecommerce operators’ biggest capital planning challenges.

It’s also important to think about the downside of demand as carefully as the upside. If one size sells twice as fast as expected, can you reorder it? If a supplement SKU suddenly takes off, can you fund more inventory without starving another part of the business? If demand underperforms, have you committed so much cash upfront that the rest of the BFCM plan becomes harder to execute?

Flexible ecommerce funding isn’t about having more money sitting around. It’s about preserving the ability to respond when reality stops matching the spreadsheet.

Plan For the Second Decision

BFCM planning usually focuses on getting the first inventory decision right. This year, apparel and wellness brands should spend just as much time planning for the second one.

Before committing inventory, decide what signals would make you reorder, pull back, shift sizes, increase marketing, or move capital somewhere else. Set those thresholds now while you still have time and options.

GLP-1 adoption is only one example of how quickly customer behavior can move. The larger move here is that your forecast doesn’t have to predict everything. Your plan has to survive being wrong. 

The best BFCM inventory plan isn’t the one that predicts every winner. It’s the one that leaves enough cash, inventory flexibility, and operating room to act when the winners reveal themselves.

FAQs

1. How are GLP-1 medications affecting ecommerce demand?
GLP-1 adoption is influencing consumer behavior beyond healthcare, including changes in apparel sizing and increased interest in certain wellness, fitness, and supplement categories.

2. How should apparel brands adjust BFCM inventory planning for GLP-1 trends?
Apparel brands should monitor demand and returns by size and SKU rather than relying only on historical size curves. Smaller initial buys and faster replenishment can also help reduce the risk of getting the mix wrong.

3. What should wellness brands watch heading into BFCM 2026?
Wellness brands should watch for changing demand across categories such as protein, fiber, collagen, hydration, and hair and skin supplements. Emerging demand should be balanced against the risk of overcommitting before the trend is fully proven.

4. Why should returns be included in BFCM demand forecasting?
Returns can distort the original demand signal, especially when customers order multiple sizes before deciding what fits. Tracking return reasons by SKU and size can give brands a clearer picture of true sell through.

5. What does flexible funding mean for seasonal inventory planning?
Flexible ecommerce funding can help brands respond when actual demand differs from the forecast, whether that means replenishing a winning SKU or preserving cash elsewhere. The goal is not simply more capital, but more room to adjust as BFCM unfolds.