AMA January '26

My guilty pleasure, the truth about supplements, and how to think about fitness as you age.

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It’s the last Friday of the month, so it’s time for our Q&A.

As a reminder, in our November AMA, I polled everyone to ask whether you’d prefer these AMAs delivered as video, audio, or text.

Text won, so I’ve written answers to all the questions. We also have audio at the bottom of the post.

Here are our questions this month:

• What are you looking forward to in the next handful of months?

• What’s your guilty pleasure?

• What’s your take on supplements if I eat a healthy diet?

• I just turned 60. How should I be thinking about fitness as I age?

• What rucking footwear do you currently recommend for use on roads and groomed trails?

• How do I balance running and rucking with joint health so I don’t get knee issues?

• You’ve mentioned mobility work a couple of times—what’s your routine like and how do you build one?

• How effective are high‑intensity light therapy lamps (10,000+ lux) as an alternative to early‑morning natural sunlight, when the latter is difficult to get because of the climate, my schedule, etc?

• Any recommendations around a good meal kit/food delivery service?

Quick housekeeping

• Thanks to our partners!

  • Montana Knife Company. I’ve been carrying MKC knives into the wilderness for years. They’re bombproof, razor sharp out of the box, and made in Montana. My everyday carry: The Mini Speedgoat 2.0. Check them out here and mention you heard about MKC from Two Percent. MKC knives sell out quickly, but here’s what’s currently in stock.

  • Function Health, which offers 5x deeper insights into your health than typical bloodwork. You’ll learn critical information that can guide you into feeling better every day. It helped me identify a mineral insufficiency. Go to my page here to sign up, receive a discount, and pay just $340.

What are you looking forward to in the next handful of months? -Diana

Two things.

First, finishing my book about mindset and mental health—the book I did the 850-mile hike for.

Second, the release of my book Walk With Weight: The Definitive Guide to Rucking.

I’ve been hitting the podcast circuit to talk about Walk with Weight (episodes drop when the book does), and it’s been a blast. I’ve had some great discussions and all the hosts I’ve talked with think the book will genuinely help people, which is exactly what I hoped for.

If you pre-order a copy here, you’ll get 15% off, and I’ll sign it.

What’s your guilty pleasure? -Julia

Diet soda. Final answer.

I love diet soda. Always have, always will.

I’m not quite at the Trumpian 12 Diet Cokes a day level, but I’m closer than I should admit.

People worry about diet soda: artificial sweetener, chemicals, etc.

I’m not going to tell you that diet soda is good for you. But I will tell you it doesn’t seem bad for you. Human research consistently suggests that diet soda is neutral for health.

• Artificial sweeteners don’t show meaningful risk in the amounts even the most extreme diet soda addict would drink. In fact, you’d die from all the water in diet soda before the artificial sweetener caused an issue. Early studies from the 1970s linked saccharin to bladder cancer in rats, but we learned the mechanism doesn’t apply to humans¹.

• Some wellness podcasters have discussed how artificial sweeteners may disrupt the gut microbiome. But, as my friend Tamar Haspel pointed out, “the gut microbiome has become the conspiracy theory of nutrition: It’s where people go to prove something’s dangerous when there’s really no evidence that it is.” To my knowledge, human studies haven’t shown anything consistent or concerning.

“Just drink water,” some will say. Well, sure. Also: Only eat vegetables and lean meat, never add salt, never eat sugar, and, while you’re at it, seal yourself in a bubble and never enjoy anything.

You get my point. Water isn’t a realistic swap for diet soda. The entire point of diet soda is to replace sugar-sweetened soda with something people actually like that has no calories and doesn’t harm health.

As Tamar wrote: “Should we let perfect be the enemy of perfectly okay?”

She wrote a particularly killer piece about diet soda for the Washington Post. You should read it. (Cracks another Diet Dr. Pepper, clicks link).

What’s your take on supplements if I eat a healthy diet? -Luke