The most consequential thing to happen to the American food system in the past two years arrived as a weekly injection. As of late 2025, roughly one in eight U.S. adults reported taking a GLP-1 medication for weight loss, roughly double the share from a year earlier. This class of weight-loss drugs is now delivering the one thing two decades of climate policy never could: a voluntary, durable reduction in how much carbon-intensive food Americans eat.
What GLP-1s Are Doing to Food Demand
GLP-1 drugs like semaglutide and tirzepatide suppress appetite through the gut-brain axis, producing average body weight reductions of about 15% in clinical trials, driven mostly by people eating less: adults on these medications consume roughly 21% fewer calories and cut their grocery spending by roughly 5–6%, per peer-reviewed research from Cornell University and Numerator.
Wall Street has already repriced the consequences — JPMorgan estimates the trend could erase $30–$55 billion in annual U.S. food and beverage sales as soon as 2030, when it expects about 25 million Americans to be on treatment (up from roughly 10 million today). Goldman Sachs estimates the 2035 user base at nearly 70 million, or about one in five adults.
The revenue hit is only the visible half of the story; the same pullback is rippling upstream, into the fields, feedlots, and water tables that supply all that food.
Where Food-System Emissions Actually Come From
The reason that withdrawal matters for the climate is because food’s emissions are concentrated. Food production generates roughly a third of global greenhouse gas emissions, and that footprint skews heavily toward one category: meat. Animal-based foods produce more than half of all food emissions. Beef is the extreme case, with a carbon footprint roughly sixty times that of beans.
This is where the demand shift becomes a climate story. The categories GLP-1 users give up first sit at the very top of that ranking, and clinical data shows they cut the most carbon-intensive foods — like red meat, ultra-processed snacks, and sugary drinks — rather than trimming calories evenly.
GLP-1 users are voluntarily adopting close to the diet that federal guidelines have recommended for years: less red meat, less sugar. When researchers modeled that shift across the U.S. population, food-system emissions fell 22%–32%. No carbon price, farm bill, or UN summit has moved demand in that direction at this speed.
How “Big Food” Is Restructuring
The companies with the most revenue at risk are moving first. Major manufacturers are reformulating for the GLP-1 consumer with smaller portions, more protein, and less sugar and refined starch, which shifts the composition of the American food supply toward lower-emission inputs. The farm system is starting to follow: corn and soybean planting projections have softened, and the U.S. cattle herd has hit a 75-year low, according to USDA data. Buying less food wastes less of it, and the roughly 700 million tons of CO₂ equivalent lost annually to food-system waste scales down with the volume.
For investors, the durability is what matters. We’re watching demand-side contraction in the single most emissions-intensive corner of the food economy, driven by consumer behavior rather than regulation. That makes it stickier than a policy that can be repealed and faster than a technology that has to be built — and the repricing rewards whoever positions before it finishes rather than after. Protein innovation, nutrient-dense formats, and the agricultural systems that supply them are where the demand is going.
The Bear Case
This thesis could break in a few places. GLP-1 adoption could plateau well below projections due to cost, access, side effects, or the simple difficulty of long-term adherence. Food companies could claw back lost calorie volume by engineering a new generation of ultra-processed products built for smaller stomachs — a reformulation risk that bears watching. Agricultural systems contract slowly, and a single year of low cattle inventory does not make a trend.
Each of those risks bears on how big and how fast the shift is, not on whether it happens. Adoption could disappoint and the supply chain could lag, but none of that puts calories back on American plates. The signal is already in the spending data and on the earnings calls. Waiting for certainty mostly means arriving after the repricing is done. Investors who treat this as a passing diet fad are calibrating to a baseline that no longer exists.
The larger lesson sits above the food system. The most powerful climate shifts are starting to arrive from outside the climate economy entirely, carried in by health, consumer behavior, and markets that were never trying to cut emissions. Investors who watch only the climate beat will keep being surprised by the ones that come from everywhere else.
The opinions expressed in Fortune.com commentary pieces are solely the views of their authors and do not necessarily reflect the opinions and beliefs of Fortune.
The post Tenzin Seldon: The GLP-1 boom is the biggest climate story no one is pricing in appeared first on Fortune.
