I NEVER THOUGHT AIRLINE FOOD could be so enticing. Yet there I was, a few weeks into the Bulletproof Diet, bracing for the aroma of 135 hot breakfasts trundling down the aisle. Mustering all my willpower, I politely declined.

Maybe you’ve heard of Bulletproof coffee, a cup of java blended with butter from grass-fed cows?

I’d had some before my flight, but the Bulletproof Diet is also about fasting, so I hadn’t had solid food in 18 hours. And even if I could eat, that cart carried white rolls and pork. I needed grass-fed beef or wild salmon. They have those at the airport, right?

The Bulletproof Diet, created by Dave Asprey, is challenging. You eat 50 to 70% of your daily kilojoules from good fat. Highquality protein and vegetables fill out most of the rest. Limited carbs. No cheese. No fizzy drinks. No airplane meals.

Who would do such a thing? After years of working in tech, Asprey was pudgy and hooked on junk food. “I wanted a high-performance body and brain that could resist the distraction of food cravings without struggle,” he recalls. He says he lost 45kg – and kept it off. And so what if it’s tough? I like a challenge.

 Challenge 1: Eat Absolutely Nothing!

Well, at least for 18 hours. Asprey argues that fasting (except for Bulletproof coffee, which is perfectly okay) between 8pm and 2pm will aid weight loss.

While more research on humans is needed to confirm that 18-hour fasting will help drop kilos, rodent studies suggest it will. I’m no rat, but I found that I had less of an inclination to nibble snacks after I drank Bulletproof coffee. And when I held out, I could chow down as much as I wanted for lunch – as long as my meal was Bulletproof approved.

Challenge 2: Junk the Junk Food

 I used to mainline fizzy drinks and roll over like a dog in the presence of warm bread. But while on Bulletproof, I had to limit my daily kilojoules from sweets or starches to 5% max.

No fake sugar either. In a 2014 Japanese study, men who drank 225ml or more of diet soda a week had a higher risk of diabetes than guys who drank little to none. Sweetness may trigger your brain to expect high-kilojoule foods, which your gut will seek out eventually. At first, cake was my enemy. Then my food fixations diminished.

 Challenge 3: Fill Up (Not Out) on Fat

Asprey says that by eating most of your kilojoules from fat, you induce “ketogenesis”, a fancy term for when your body metabolises fat instead of carbs.

A 2014 study in the journal Endocrine found that people on a low-kilojoule, ketogenic diet lost more weight than those who went low-kJ only. Beyond the buttered coffee, I ate most of my fat from egg yolks, butter-topped steaks and cooking oil. I also piled on the vegetables, which are low in kilojoules. With all that protein and fibre, I started feeling fuller for longer.

Challenge 4:  Befriend My Kitchen

I won’t lie: going out to eat on the Bulletproof Diet is difficult and pricey. But if you cook at home, the plan is relatively inexpensive to pull off. Asprey’s book has recipes for beef stew, rack of lamb, baked fish, taco salad, meatballs and burgers – guy food.

Here’s the other kicker about cooking: if you’re an 84kg man, preparing food torches 465kJ in half an hour. That’s 61 more than you would burn sitting in some restaurant for the same stretch of time. As the burners fired on my stove, I was burning fat too.

SO BY NOW YOU’RE WONDERING two things: how much weight did I lose, and will I stick with the plan?  As a 102kg work-at-home type, I lost 2,25kg after 15 days on the diet. I’m sure some of that was the result of my simply not eating as much. But I also wasn’t hitting the snack drawer. (Snacks made with butter from grass-fed cows don’t exist – at least not yet.)

After about a month, I lost 5kg. Will I bulletproof myself for life? As a left-brainer, I love the geeky aspects of micromanaging my diet. As a busy guy, I like cutting the work out of breakfast (33% less meal planning!).

But if the right piece of cake appears? Here’s hoping my will turns bulletproof as well.