For many, the real meaning of Christmas lies in sharing meals with family and friends. These feasts are often extravagant in style or size (or both) and are designed without our gut microbiomes and arteries in mind: Such is their joy.

They¡¯re also often laden with tradition. My family¡¯s festive table, however, has been through a series of evolutions. My pescetarian childhood Christmas was celebrated around an enormous bowl of pesto pasta. We had a few years of the traditional roast turkey, followed by beef when it was decided a big bird wasn¡¯t worth the stress. Then the feast was vegan until last year, when my parents decided to welcome small amounts of dairy back into their lives.

All the meals were suitably celebratory, but the transition back toward dairy was notable because it echoes a shift I¡¯ve seen multiple times among my peers. Several vegetarian and vegan friends have reverted to eating meat or are considering it, while ¡ª at least in my limited experience ¡ª no one seems to be going the other way. There¡¯s also been a spate of celebrities renouncing plant-based diets too, including Lizzo, Miley Cyrus and Bear Grylls. Full disclosure: I¡¯ve been a vegetarian for the last seven years, but I sometimes eat fish, and on a few occasions, I have eaten meat. (Some might call me a flexitarian.)

It¡¯s tempting to dismiss a preoccupation with others¡¯ food choices as nosy. But it matters, at least on a macro scale. U.K. agriculture accounted for an estimated 12% of U.K. greenhouse gas emissions in 2023, a proportion that has been growing in significance as other sectors¡¯ emissions decline. And as the U.K. imports around half of its food, our diets have effects beyond those associated with domestic farming.

Looking at it from a consumption perspective, food makes up about 30% of the carbon footprint of a typical household in high-income European countries. Most of that footprint comes from animal products, with livestock farming accounting for 14.5% of global emissions. Governments seeking to reach net zero greenhouse gas emissions will have to clean up their nations¡¯ plates.

This doesn¡¯t mean that everyone must go vegan. Given food consumption is highly personal, influenced by numerous factors including culture, allergies and health, that would be an unrealistic goal. But coupled with improvements in production practices and food waste, big reductions can be achieved with small lifestyle shifts. The Climate Change Committee, an independent advisory body, has recommended that U.K. meat consumption should come down by 20% by 2030. A 2019 report written by Richard Carmichael, a research fellow at Imperial College London, for the CCC says that halving consumption of animal products by avoiding the...