Fasting & Food Miles: Does Where We Eat From Matter?

Does Local Food Have a Smaller Carbon Footprint?

"Eat local" is one of the most common environmental recommendations offered to consumers, appearing on farmers-market signage, food packaging and countless well-meaning articles.

But when it comes to food's overall climate impact, distance travelled is often not the most important factor, even though intuitively it feels like it should be.

Transport accounts for only around 5–6% of food-system greenhouse-gas emissions in widely cited global analyses, including the work of researchers such as Poore and Nemecek, who examined tens of thousands of farms and supply chains worldwide. That is a surprisingly small slice of the overall picture.

Most emissions occur earlier in the supply chain — particularly through land use change, on-farm production processes, fertiliser use and, for animal agriculture, enteric fermentation and manure management. By the time food is loaded onto a truck, ship or plane, much of its environmental cost has often already been determined.

What We Eat Often Matters More

Beef, lamb and other high-impact foods can have footprints many times larger than most plant-based foods, even before transport is factored in at all. A kilogram of beef produced next door can, in many cases, still carry a larger footprint than a kilogram of lentils shipped from the other side of the world.

Consequently, replacing a high-impact food with a lower-impact alternative can often make a considerably greater difference than simply choosing a local version of the same high-impact food. This doesn't mean food miles are irrelevant — for a small number of foods transported by air freight, such as certain out-of-season fruits and vegetables, transport emissions can become proportionally significant. But as a general rule across the whole food system, composition tends to outweigh distance.

A Common Misconception

It is worth directly naming the misconception at play here: many people assume "local" is roughly synonymous with "low-carbon." In reality, a locally grown tomato produced in a heated greenhouse during winter can have a larger footprint than the same tomato grown in a sunny climate abroad and shipped efficiently by sea. Method of production, growing conditions and mode of transport (sea freight is far more efficient per tonne than air freight) all complicate the simple local-equals-better assumption.

Where Does Fasting Fit?

Fasting reduces the quantity of food consumed over a given period. Food miles concern the distance that food travels before it reaches a plate. These are therefore largely separate variables, addressing different parts of the environmental equation.

Someone could fast regularly, as described throughout this site, but still eat highly resource-intensive, well-travelled foods on the days they do eat. Another person could eat every single day but consume a relatively low-impact, mostly local and mostly plant-based diet.

The second person could plausibly have a lower overall food footprint than the first, despite eating more frequently — a conclusion that might initially seem counterintuitive but follows directly from how emissions are actually distributed across the food system, as explored further in Agricultural Land and Water Consumption.

The Interesting Combination

The environmental question becomes considerably more interesting when the two strategies are combined rather than treated as substitutes for one another:

Eat less, and choose lower-impact foods

rather than simply:

Eat less, regardless of what is eaten.

The first approach addresses both the quantity dimension and the composition dimension of consumption simultaneously, which is a theme this series returns to repeatedly, including in Fasting vs Plant-Based Diet.

The OneYearFast Lesson

Fasting should not be promoted, or understood, as an alternative to thoughtful food choices. Skipping meals three days a week does not offset the impact of choosing carbon-intensive foods on the other four.

Instead, fasting can be considered one possible component of a broader strategy for reducing unnecessary consumption, sitting alongside decisions about what to eat, how much to waste, and where food comes from.

And the evidence gathered by food-system researchers suggests that focusing exclusively on food miles — while emotionally satisfying and easy to visualise — misses much of the environmental story that actually determines a food's footprint.

Mode of Transport Matters More Than Distance Alone

Even within the small slice of emissions attributable to transport, not all miles are equal. Sea freight is remarkably efficient per tonne of cargo moved, which is why a great deal of the world's food travels enormous distances by ship with a comparatively modest emissions cost. Air freight, by contrast, carries a much higher emissions cost per tonne, but it is used for only a small share of global food trade, generally reserved for highly perishable items such as certain berries, asparagus or cut flowers that would spoil during a long sea voyage. Road transport for shorter, final-mile distances sits somewhere in between, depending on vehicle type and load efficiency.

This means that a piece of fruit flown from overseas can carry a genuinely outsized footprint from transport alone, while a similar piece of fruit shipped by sea, even from much further away, may add relatively little to its overall footprint. Distance, in other words, is a poor proxy for transport emissions; mode of transport is the more decisive factor.

A Practical Illustration

Imagine two shoppers buying dried lentils. One buys lentils grown a short drive away; the other buys lentils grown on another continent and shipped by sea. Given how small transport's share of total emissions tends to be for a low-impact, non-perishable food like dried lentils, the difference between these two purchases is likely to be minor compared to, say, either shopper occasionally substituting a portion of red meat for lentils in their weekly meals. This is the essence of the food-miles argument: distance is rarely the lever worth pulling hardest, even though it is often the most visible and emotionally intuitive one to consumers standing in a supermarket aisle.

Key Takeaways

• Transport typically makes up only around 5–6% of food-related greenhouse-gas emissions in global estimates.
• Most food emissions arise from production, particularly land use and farming processes, not from distance travelled.
• "Local" does not reliably mean "low-carbon"; production method can outweigh distance.
• Fasting addresses quantity of consumption, while food miles concern one narrow aspect of production logistics.
• Combining reduced consumption with lower-impact food choices is likely more effective than either approach alone.