I Ate Only Tempeh For a Month, Here's What happened…

By Dr. Ando Ahnan-Winarno aka The Protein Doctor, co-founder of Better Nature and protein scientist

Comedian Mo Gilligan just spent 28 days eating nothing but fried chicken for his Netflix documentary: Big Chicken: A Fast Food Conspiracy, and by the end of it, he wasn't feeling great. His energy was gone, mood flat. It's a really interesting watch, and it reminded me of something I did myself.

Long before Better Nature existed, I did my own month-long experiment where I ate tempeh as my only protein source for a month. And the whole point of it was to prove a point I'd been arguing with my friends for months.

Why I did it

I'd learned the nutritional benefits of tempeh in real depth by this point, and I genuinely think it's the best source of protein. It has all the essential amino acids, it's high in fibre, it's gut-friendly, high in antioxidants, high in vitamins and minerals. But I was living in Indonesia at the time, and my Indonesian friends simply wouldn't believe me that tempeh was that healthy. The general view was, it's food of the poor, a humble food, your plan B if you can't afford meat.

So I wanted to prove them wrong. I said, look, I'll eat only tempeh as my protein source for the whole month, and I'll still do my weightlifting. I wanted to show them I'm healthy, I'm still in shape, and that tempeh could support lean muscle growth too, not just keep me alive. I called it the tempeh challenge.

What I actually ate

Only tempeh as my protein, every meal, three times a day, for a full month. I still ate carbohydrates, rice and veg, but the protein was always tempeh. Mornings I'd usually have leftover rice from the night before, so rice and tempeh, and I kept switching up how I cooked it so it never felt too repetitive: sometimes grilled, sometimes as a soup with veg, sometimes seasoned with turmeric, coriander and garlic, sometimes just plain with salt and oil then grilled, sometimes with soy sauce.

I did a rough measurement too. I think every day I ate about a fist-sized amount, roughly 200 grams, about the size of our Better Nature Tempeh.

The first week was easy. By the end of week two I was bored, not sick of it, just bored, and the different ways of cooking it helped me push through the final two weeks.

What I noticed

I might be biased, but I genuinely felt good throughout. Less of the usual muscle soreness after heavy lifting, sleep was fine, recovery felt quick, digestion was completely normal. No bad side effects at all, which is exactly what I was hoping to prove.

What I was actually testing

As a protein scientist, I wanted to know whether tempeh would compromise muscle growth or genuinely support it. There's a real risk in "protein maxing" with a source that's high in saturated fat, you build fat alongside muscle without realising it. Tempeh didn't come with that trade-off.

There's also a persistent fear about soy and isoflavones, when isoflavones are actually the main health-promoting compound in the bean. On protein itself, tempeh sits around 22g per 100g against chicken breast's 25g, close enough to be genuinely comparable, which lines up with the 44g per 200g pack you'll find on ours.

The assumption that plant protein can't sustain an active lifestyle is wrong. It was never really about plant versus animal; it's about whether your needs are met: protein, essential amino acids, fibre, key vitamins and minerals. Tempeh brings a lot of that in one place.

WOULD I DO IT AGAIN

No, and that's the point! I love tempeh, but I want variety, not repetition.What actually surprised me, looking back, is that I couldn't imagine doing this same month with eggs, chicken breast or whey. Tempeh's versatility got me through, and honestly, it's close to my heart as an Indonesian.

If you're curious, why not just swap one chicken dish for tempeh. My go-to is a five minute stir fry, tempeh cubed or torn, teriyaki sauce, chopped veg, served with rice. You can find lots of great recipes here.