Other than my dairy kryptonite however, I’ve since had to be “that guy” at numerous parties, BBQs and family get-togethers. You know the one — the person who has to pretend they can ignore the delicious smell of fried chicken, or the succulent chargrilled burgers.

I’ll be brutally honest: it can be difficult. There’s a fair amount of behavioural science evidence that it is important for people to act in ways reasonably consonant with the identity that they have for themselves. And this is something I found because I’ve toyed back and forth between whether not eating meat is actually going to make a difference to the world. So I was intrigued to read about The Economist’s proposal for a “banana index” that compares the relative carbon impact of different foods.

At first review, it’s quite a simple but clever idea. After all, it can be hard to compare emissions of meals that are equally nutritious but differ in weight, calories, and protein. By indexing these metrics to the humble banana, we get a sense of how different foods stack up against each other.

Unsurprisingly, beef scores poorly on the banana index. Producing one kilogram of beef mince causes as many emissions as 109 kilograms of bananas. Adjusting for nutritional value, beef’s banana score falls to 54, while by protein, it scores seven. In contrast, plant-based alternatives to meat score much lower on the index. A meat-free burger, for instance, scores just one-fifth of the emissions of bananas per gram of protein.

Of course, the banana index has its limitations. For one, it doesn’t capture other environmental impacts, such as land and water use, which can be significant for certain foods. Beef, for example, is notorious for its high water use and land conversion rates. Moreover, the index relies on average emissions for a given food, which can vary widely depending on how it’s produced and transported.

The index also assumes that all foods are equal in terms of nutritional value, which is not necessarily the case. While it’s true that plant-based foods can be just as nutritious as meat, they often require more careful planning to ensure a balanced diet. For example, while tofu is a good source of protein and meat alternative, it can be lower in certain nutrients. This means that simply comparing emissions by weight or protein may not tell the full story of a food’s impact on health and the environment.

That being said, the banana index is a useful tool for starting a conversation about the relative carbon impact of different foods. It underscores the fact that meat production is a significant contributor to greenhouse gas emissions and that plant-based alternatives can be much more climate-friendly.

But we shouldn’t stop there. We need to also consider the land, water, and energy inputs that go into food production, as well as the nutritional value of different foods. Ultimately, what we eat is just one piece of the puzzle when it comes to reducing our carbon footprint. We also need to look at how we produce food, how we transport it, and how we reduce waste.

But by paying attention to what we put on our plates, we can make a real difference in the fight against climate change by reducing our emissions. The banana index may not be perfect, but it’s a step in the right direction.