McDonald's shares rose 6% following a third-quarter earnings beat, though U.S. comparable sales slipped 0.2% due to fewer guests. Investor Daniel Mahncke identifies GLP-1 weight-loss drugs as the company's most significant threat in decades, estimating current impact at roughly 1% of sales but warning it could escalate to 10%. Research indicates households using these drugs spend about 8% less at fast-food chains within six months. McDonald's President Skye Anderson noted that approximately 30 million Americans use GLP-1s, with 84% of those households visiting McDonald's. Eli Lilly's Zepbound revenue surged 48% to $5.3 billion in the third quarter, and the FDA recently approved its once-daily pill, Foundayo. Analysts have cut EPS estimates for 2026 through 2028 by an average of 3.5% to 7.6% over the past year as concerns about sales volume grow. The company's franchise model shifts much of the risk to owners, whose cash flow has dropped about 10% from post-pandemic peaks. A 10% sales hit would reduce a typical restaurant's cash flow by $400,000 against a baseline of $500,000, with minimum rent payments limiting downside flexibility. McDonald's operates at 20x forward earnings, below its five-year average, and plans a value menu launch in early 2027 to counter headwinds. Management has provided $8.5 billion in rent relief and capital support through 2036 to aid franchisees, but Mahncke suggests further concessions may be needed if the sales decline approaches the higher end of estimates. The stock trades at a discount that fits a 1% impact scenario but would likely drag estimates lower if the 10% case materializes, prompting investors to wait for guest count recovery before buying.