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Week Twelve - Eat Less

Save 356 kilograms CO2e per person per year

· Weekly experiments

My preschooler

- Today at daycare, there was no food. No morning tea, no lunch, no afternoon tea, no happy snacks. I got upset and said I was hungry but the teachers ate all the food and I didn't get any.


- I'm so proud. You've reached a new developmental milestone. Lying!

An empty dinner plate weeps

The Great Diet Debate

Like my child, I don't like going hungry. I find diets soul-destroying, life-sapping and completely ineffective. I have friends and colleagues who have been dieting their entire lives. I assume they do it as a hobby or to support the entrepreneurial spirit that invented superfoods, slimming soaps and the swamp diet. It can't be to lose weight, because while each new regime works for a week, from one year to the next, they're all getting heavier. This is the real magic of the diet industry. The client base always comes back.

Most doctors disapprove of the modern 'diet' for this reason. My doctor talks about 'diet' in terms of the general food I eat and says I shouldn't make any change I can't maintain for the rest of my life. It's good advice, given that almost 2 in 3 Australian adults are overweight or obese. My mid-life checkup showed I need to lose belly fat, so I thought I'd look at one of the better-researched fads, the 5:2 Fast. With much of the world fasting for health, spiritual, religious or cultural reasons, this might also be a powerful way to cut carbon dioxide and equivalent emissions (CO2e).

Is it a fad or a way of life?

Supporters say that feed-and-famine was the natural cycle for our ancestors, that many religions and cultures have successfully used fasting for thousands of years and that it has mental, spiritual and health benefits. Critics say it's a form of disordered eating, it's unhealthy long-term and it's too difficult to maintain.

I won't weigh in on any of that. I'll simply explore the carbon implications for an adult who has decided to regularly fast. Make sure you check with your doctor before making any major dietary change and please don't consider fasting if you're sick, pregnant or still growing.

What is it like to fast?

The 5:2 program requires people to limit their daily intake to a modest 2100 - 2500 kilojoules on two days and eat normally for the other five. I picked two non-consecutive days during the week. In the past, skipping meals made me want knaw my own arm off (or better still, someone else's). This time, the hunger came and went and I got on with my work. I avoided days when I had a cycle commute as cycling makes me ravenous. I managed a light workout with no trouble. Perhaps my body has changed over time, or perhaps I've simply found a good reason to do it.

A low kilojoule fasting meal of smoke salmon and salad

A low-kilojoule '5:2 fasting' dinner.

How much CO2e did I save by fasting?

My 'fasting' meals were pumpkin and lentil soup on one day and smoked salmon salad on the other, with some nuts and miso soup as snacks. Fish has a higher carbon footprint than lentils, but it's lower than most meats and I only ate 150 grams. The fasting days generated a low footprint of 0.31 and 0.51 kilograms CO2e, which is less than usual. However, I fasted at the start of the week when I tend to eat a modest vegan diet anyway, so the change is marginal. Over a year, eating like this would shave 50 kilograms from my total food footprint of 1.05 tonnes CO2e.

How much CO2e would the average Australian save?

The results are more interesting for a standard Australian diet. Thanks to information provided by Dr Stephen Clune of Sustainability Research and Design, I ran a carbon analysis on a comparison 'average Australian' family. The Molloys took part in a photographic study called 'Hungry Planet - What the World Eats'. Their diet delivers similar kilojoules to mine for around 1.4 tonnes CO2e each year. Assuming they eat meat and dairy every day in a fairly consistent pattern, switching to a 5:2 diet consisting of one egg, vegetable protein and a little fish could save 356 kilograms CO2e per adult per year.

If you currently eat meat and dairy every day, this is a valid way to cut your carbon footprint. It may come easier for those who don't want to learn new habits (eg. vegan cooking) and it may appeal to those who want to save time, lose weight and improve their health.

Photo of what an average family like the Molloys eat each week

The Molloys are pictured with their weekly groceries. Over a year, the carbon footprint from this food is around 1.4 tonnes per person. This doesn't include the alcohol and other drinks. I'll come back to those at another stage.

When fasting backfires

Many fasting diets don't require you to omit food altogether, but rather to eat a high-protein, low-kilojoule meal on your 'fast' days. Depending on what you choose, you could inadvertently increase your carbon footprint by doing this. For instance, the 5:2 recipes of a cottage cheese breakfast + sashimi fish dinner came in at 1.45 kilograms CO2e and the egg breakfast + steak salad dinner delivered a whopping 3.41 kilograms CO2e. I can stuff my belly with vegan food all day for less than 1 kilogram CO2e. If you're fasting for the sake of the planet, stick to vegetable protein, with the occasional egg or a little fish or chicken. For guidance about fasting, try researching 5:2, Alternate Day Fasting or religious fasting.

Less is more

Fasting fits a clear theme developing in my project. Carbon-cutting options can be complex and overwhelming and it's difficult to find reliable numbers, but a simple reduction almost always works. I've so far saved carbon by throwing out less waste, flying less, heating my house less and feeding less meat to my dogs. All of these were easy to do and saved me money. Similarly, if done the right way, regular fasting could be a simple way to cut carbon and may provide you with other benefits. If you're not keen on fasting, check in over the next few weeks as I test other ways to reduce your carbon foodprint.

Spreadsheet calculations, reference list and data discussion in the 'Notes' section, Week Twelve.