By Ian Gleghorn, Founder of TESTO | Reviewed by Jenni Lane, Natural Health Formulation Specialist

Most men don’t notice it happening. You’re not suddenly different one morning. It’s gradual — a slight drop in energy here, a bit less drive there, training sessions that take longer to recover from. The kind of slow fade you chalk up to being busy, or stressed, or just getting older.

Here’s what’s actually going on.

From around 35, your total testosterone drops at roughly 0.8 to 1% per year. That sounds manageable. But free testosterone, the form your body can actually use, declines faster: around 1.5 to 2% per year. That’s because SHBG (sex hormone-binding globulin) increases with age, binding up more of your testosterone before it can do anything. By the time you’re 50, the gap between what you have and what’s available to your cells is significant.

I learned all this properly when I was working with Jenni Lane, our formulation specialist, developing TESTO. She’s been in natural health for over 20 years, and she was the one who explained why so many men feel the effects more sharply in their 40s and 50s than the numbers alone would suggest.

The good news: there’s a lot you can do about it, without a prescription.

Resistance training

This is the single most evidence-backed lever you have. Compound movements, squats, deadlifts, rows, presses, stimulate testosterone response and help preserve lean muscle that naturally wants to disappear after 40.

You don’t need to train like you’re 25. Three to 4 sessions a week of genuine effort, with progressive overload over time, is enough to make a meaningful difference. Consistency is the variable that matters most. A few months of hard training followed by nothing doesn’t hold the gains.

I’m 60. I train 4 days a week, work around a couple of old injuries, and I still feel the difference when I’m consistent versus when I let it slip.

Sleep

Most testosterone production happens during sleep, specifically during deep sleep cycles. Cut that short and you’re not just tired, you’re cutting off the primary production window.

Seven to 9 hours isn’t a luxury. For men over 40, it’s maintenance. Research on sleep deprivation and testosterone is consistent: even a week of poor sleep measurably reduces levels in healthy men.

If your sleep is broken, fix that before you look at anything else.

Manage cortisol

Cortisol and testosterone have an inverse relationship. When one goes up, the other tends to come down. Chronic stress, overtraining, poor sleep, and alcohol all raise cortisol. Over time, this creates a drag that compounds the age-related decline.

This doesn’t mean eliminating stress, that’s not realistic. It means building genuine recovery into your week. Physical recovery matters. So does mental recovery.

Nutrition and key micronutrients

You don’t need a special testosterone diet. But a few things matter more than most men realise.

Zinc is involved in testosterone synthesis. NZ soils are notoriously low in it, which means most of us aren’t getting enough through food alone. Vitamin D, also deficient in a large percentage of NZ adults, plays a role in hormonal function across the board.

Getting these from food where possible is ideal. Real food, adequate protein, not restricting calories to the point where your body thinks it’s under threat. That’s the foundation.

Where a supplement fits in

When Jenni and I were developing TESTO, the brief was specific: 7 evidence-backed ingredients, every dose shown on the label, no proprietary blends. We wanted something that worked alongside the fundamentals above, not instead of them.

TESTO isn’t a replacement for training, sleep, or good nutrition. Nothing is. But for men who’ve got the basics in place and want targeted nutritional support, it fills gaps that are genuinely hard to get from diet alone. That includes zinc and vitamin D3, plus ingredients like icariin (from horny goat weed), which has been used in traditional medicine for centuries and has a growing body of modern research behind it. Jenni selected each ingredient based on the evidence, not because it sounded good on a label.

If you’re 40+ and starting to feel the slow fade, start with the basics. Then decide whether you want additional support on top.

TESTO comes with a 90-day guarantee. If it’s not working for you, you get your money back.

[Try TESTO from $1.99/day]