Fasting & Eating Less: Does It Reduce Emissions?

The Simple Question

If we eat less food, do we create fewer greenhouse-gas emissions?

In principle, potentially yes.

But the answer is more complicated than simply multiplying calories by an emissions factor.

Food production accounts for around 26% of global greenhouse-gas emissions in widely cited global estimates.

Therefore, changes in food consumption can potentially have environmental consequences.

Calories Are Not Equal

One of the biggest problems with calculating the environmental effect of fasting is that a calorie does not have a fixed carbon footprint.

The emissions associated with foods vary enormously.

A calorie obtained from beef has a very different environmental history from a calorie obtained from beans or grains.

Consequently:

Eating 500 fewer calories of beef and eating 500 fewer calories of vegetables do not represent equivalent environmental changes.

The Compensation Problem

There is another issue.

Suppose someone normally consumes 2,000 calories every day.

They begin fasting three days per week.

If they subsequently eat 2,850 calories on each of the four feeding days, their average weekly intake could remain roughly unchanged.

In that situation, fasting has changed the timing of food consumption without necessarily reducing the amount.

The environmental effect could therefore be much smaller than expected.

Genuine Reduction vs. Redistribution

This distinction is fundamental.

Fasting can redistribute food consumption.

Or:

Fasting can reduce food consumption.

They are not the same thing.

For an environmental benefit to arise from reduced consumption, the total quantity of food consumed over time needs to decline rather than simply being compressed into fewer eating days.

What Would We Need to Measure?

A meaningful OneYearFast experiment could record:

• Total food consumed
• Calories
• Food categories
• Animal vs. plant foods
• Food waste
• Fasting days

The annual totals could then be compared with a person's previous eating pattern.

That would provide a much stronger answer than simply assuming that fasting reduces emissions.

The Important Conclusion

Fasting may reduce food-related emissions if it genuinely reduces food consumption.

But fasting does not automatically equal a smaller carbon footprint.

The environmental outcome depends on what happens to total consumption.