Do Ozempic and Mounjaro Have a Climate Benefit?

Jill from Putney has been taking Mounjaro for four months. She is standing in the meat aisle of her local Waitrose, browsing the beef. She picks up a large steak, considers it briefly, and puts it back on the shelf. Not for health reasons. Not out of any concern about carbon footprints. She simply knows she won’t be hungry enough to eat it all. So she buys a smaller chicken breast instead.

Multiply that moment by 4.3 million — the number of Britons who, according to new YouGov research published today, have now used GLP-1 weight-loss medications — and something remarkable starts to take shape. Not a public health campaign. Not a government dietary intervention. Not a food labelling scheme. Just an incidental, uncoordinated, nationwide shift in what people eat. And a potential reduction in the carbon footprint of British food consumption that nobody is talking about.

Climate researchers have spent years making the case that what people eat matters at least as much as how they travel or heat their homes. Governments have broadly ignored them. Carbon-labelling schemes have gone nowhere. Meat taxes remain politically unthinkable. And in the unexpected mechanics of a drug designed to treat obesity and type 2 diabetes, something that policy has consistently failed to achieve may be happening anyway.

The question that remains largely unquantified is: how much?

The revolution in the trolley

YouGov’s new Health and Wellbeing Tracker, drawn from a nationally representative sample of 303 GLP-1 users surveyed in February 2026, paints a granular picture of how these drugs are reshaping what Britain buys and eats. The headline spending numbers have attracted considerable attention from the food and grocery industries. Users spend on average 11 per cent less on their weekly grocery shop and 19 per cent less per month on takeaways than before starting treatment. Even after stopping the medication, the habits appear to stick: former users still spend around seven per cent less on groceries and nine per cent less on takeaways each month.

What the food industry sees as a threat, a climate analyst might read differently. Nearly two-thirds of current users say they eat fewer snacks. More than a third are eating more vegetables. Alcohol consumption is falling. Takeaway orders — typically built around the most carbon-intensive foods on any menu — are down sharply.

Ag Hoffmann, YouGov’s Lead Healthcare Director, framed the market disruption in stark terms. “The rise of GLPs is having a huge impact on the grocery and takeaway market,” he said. “Whilst the number of users is relatively low at the moment, this is only going to increase in the future, creating both opportunities and threats to the wider market from QSRs to grocers.” He is talking about profit and loss. But the same data reads very differently through a climate lens.

The clinical reality underpinning all of it is this: people on GLP-1 drugs naturally eat somewhere between 25 and 35 per cent fewer calories — around 500 fewer calories a day, according to Tom Curtis, clinical head of obesity at weight management service Voy. The drugs work by suppressing appetite, slowing digestion, and altering the brain’s hunger signalling pathways. The result is not just less food. It is a fundamentally different relationship with food. And the foods people are gravitating towards — nutrient-dense, high-protein, smaller-portioned — are, almost without exception, less carbon-intensive than the foods they are leaving behind.

Why it matters what you cut

To understand why any of this has climate significance, it helps to know how wildly different foods are in terms of the greenhouse gases they produce. The numbers are not intuitive.

In 2018, Joseph Poore and Thomas Nemecek published what remains the most comprehensive analysis of food systems ever conducted, drawing on data from 38,700 farms across 119 countries and 1,600 processors, packaging types and retailers. The paper, published in Science, took five years to complete. Its findings were stark enough that Poore, who was based at the Department of Zoology at the University of Oxford, stopped eating animal products himself partway through the research.

“A vegan diet is probably the single biggest way to reduce your impact on planet Earth,” Poore told the Guardian when the study was published. “Not just greenhouse gases, but global acidification, eutrophication, land use and water use. It is far bigger than cutting down on your flights or buying an electric car.” He added something that is particularly relevant here: “Avoiding consumption of animal products delivers far better environmental benefits than trying to purchase sustainable meat and dairy.”

The data tells you why. Producing a kilogram of beef generates roughly 60 kilograms of CO2 equivalent, according to the Poore and Nemecek dataset as analysed by Our World in Data. Chicken sits at around six kilograms of CO2e per kilogram — a tenth of the impact. Cheese carries about 13 kg CO2e per kilogram. Even crisps and processed snacks, categories that GLP-1 users are cutting sharply, have an industrial carbon footprint of approximately 3.08 kg CO2e per kilogram. Vegetables, by contrast, sit between roughly 0.5 and 2 kg CO2e per kilogram.

The arithmetic of switching from beef to vegetables is therefore not a modest environmental improvement. It is, per kilogram of food, a reduction by a factor of 30 to 60. Swap crisps for broccoli, and the saving is still roughly tenfold. Carbon Brief’s analysis of the Poore and Nemecek data found that the climate impact of plant-based foods is typically 10 to 50 times smaller than that of animal products. The trajectory of GLP-1 users’ diets moves, consistently if not completely, in that direction.

Running the numbers

For this article, we have used Claude, Anthropic’s AI assistant, to model the aggregate carbon implications of the dietary changes documented by YouGov, drawing on food systems data and UK greenhouse gas emissions figures. The exercise is necessarily indicative. It works from a baseline, applies adjustments for quantity and composition, and produces a range rather than a precise figure.

The starting point is the UK’s average food-related carbon footprint: approximately 2.2 tonnes of CO2 equivalent per person per year. That figure covers the full supply chain — agriculture, processing, transport, packaging and waste. Food accounts for roughly 19 per cent of the UK’s domestic greenhouse gas emissions, and closer to 30 per cent when emissions embedded in imported food are counted.

Applied to 4.3 million GLP-1 users, a conservative 20 per cent reduction in food consumption produces a quantity saving of roughly 0.44 tonnes CO2e per person per year. But the composition effect is what makes the number more interesting. GLP-1 users are not cutting average foods. They are cutting snacks, processed food, takeaways, heavy meat and high-fat dairy — the most carbon-intensive corners of the grocery basket. Applying a carbon intensity multiplier of around 1.3 to 1.4 to reflect that concentrated reduction raises the per-person saving to approximately 0.55 to 0.65 tonnes CO2e per year, before accounting for the modest carbon associated with increased fish consumption.

The central estimate, after adjustments, is around 0.5 tonnes of CO2e per person per year.

Across 4.3 million users, that produces an aggregate saving in the region of two million tonnes of CO2 equivalent per year — with a plausible range of 1.4 to 2.8 Mt CO2e depending on the assumptions used.

In 2024, total UK territorial greenhouse gas emissions were estimated at 371 million tonnes of CO2 equivalent, according to the Office for National Statistics. Two million tonnes is roughly 0.5 per cent of that total. As a standalone number it sounds modest. Set against the food system specifically — which accounts for around 19 per cent of UK domestic emissions — it represents about 1.3 per cent of the sector’s entire annual output. For context, it is roughly the equivalent of removing 900,000 average petrol cars from UK roads for a year. Achieved not by a single policy, subsidy, or campaign. Achieved as a side effect of medical treatment.

The numbers that should make policymakers sit up

The figure of two million tonnes is already significant. What comes next is more so.

YouGov’s data shows that 14 per cent of British adults — 7.6 million people — would consider using GLP-1 medications in the future. UCL research published earlier this year found that 3.3 million people who had not yet taken weight-loss drugs said they would be interested in doing so within the next year. A pill formulation of Wegovy — far easier to administer than the current injectable — has been submitted for regulatory approval in both the UK and the EU. If approved, it could change the economics and accessibility of these treatments substantially.

If that potential user population joins the current 4.3 million, the combined annual dietary carbon saving could rise to somewhere between 5.5 and 8 million tonnes of CO2 equivalent per year. That is the rough equivalent of removing between 2.5 and 4 million petrol cars from British roads permanently.

The Agriculture and Horticulture Development Board’s analysis of GLP-1 trends, published in early 2026, drew on US data from a Cornell University and Numerator study showing that households with at least one GLP-1 user reduced their total grocery spend by around six per cent within six months of starting treatment. The AHDB noted that the UK is following a similar trajectory, with high-fat, indulgent products declining and high-protein, nutrient-dense categories growing.

Where the story gets complicated

None of this should be taken as straightforward good news for the planet, and anyone presenting it that way would be getting ahead of the evidence.

The food industry’s response to GLP-1 users has been swift, and not necessarily in the direction climate scientists would recommend. Morrisons, M&S, Co-op, Asda and Sainsbury’s have all launched dedicated GLP-1-aligned ready meal ranges in 2026. Many of these products are classified as ultra-processed foods. A GLP-1 user who replaces a bag of crisps with a proprietary protein-enriched ready meal has improved their diet by many measures. They may not have improved it by much from a carbon perspective.

The profile of who is currently on these medications also matters. Around 95 per cent of UK GLP-1 users have a household income exceeding £100,000, according to Lumina Intelligence, and the majority are concentrated in London, where obesity rates are among the lowest in the country. It is an affluent, urban, already health-conscious cohort. Their pre-GLP-1 dietary baseline may already be less carbon-intensive than the UK average, which would reduce the net compositional saving in practice.

The drugs themselves are not carbon-neutral. Injectable weight-loss medications require cold chain logistics, single-use delivery devices and pharmaceutical manufacturing — none of which is zero-carbon. A rigorous lifecycle analysis of GLP-1 medications as an environmental intervention has not been conducted. It would be a worthwhile exercise.

Finally, the most compelling dietary changes occur during active treatment. The effects moderate after users stop taking the drugs, though the YouGov data suggests they do not disappear entirely. The long-run sustained saving across the full user population is likely lower than the in-treatment figure.

An effect that has yet to be fully measured

There is a broader point here that runs beyond the specific numbers.

For the better part of two decades, climate researchers have argued that dietary change is one of the most powerful levers available to reduce food system emissions. The Food Foundation has noted that UK food emissions have fallen at only half the rate of the wider economy, and that without structural change they will be four times the necessary level by 2050. The food system, as Poore and Nemecek’s paper calculated, generates around 26 per cent of global anthropogenic greenhouse gas emissions.

Policy has consistently failed to address this. Meat taxes remain toxic as a political proposition. Dietary guidelines have had negligible impact on consumption patterns. Carbon labelling on food packaging, widely recommended by researchers, has never been mandated in the UK.

GLP-1 medications are, of course, not a climate policy. Nobody is prescribing Wegovy to save the planet. These drugs exist to treat serious metabolic disease. The environmental dividend is incidental, a side effect of a side effect. But the scale of adoption, and the direction of dietary change it is producing, may yet make it one of the more consequential unintentional climate interventions of the decade. The carbon implications have barely begun to be measured.

Jill from Putney wasn’t thinking about CO2 when she put the steak back. But the numbers suggest she may have done more for the atmosphere than most people who were.

This article was researched using Claude from Anthropic, which was used to synthesise published data and construct the carbon modelling framework. The CO2e estimates are modelled projections based on current-user assumptions and should be treated as indicative ranges rather than precise measurements.