For men aiming to preserve strength, drive, and vitality into their later decades, testosterone is often top of mind. As levels of this key hormone gradually decline over time, many search for natural ways to support healthy levels without jumping straight to hormone replacement therapy.
In a recent deep-dive experiment, YouTuber Lawrence from Fit and 50 set out to test one possible solution: switching to a high-fat diet. Backed by a new meta-analysis that connects dietary fat intake to testosterone levels, his experience sheds light on how nutritional choices could impact hormonal health — especially for men over 50.
Let’s unpack the science behind testosterone and fat intake, explore Lawrence’s personal results, and offer tips for safely experimenting with dietary changes to optimize hormones.
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The Problem: A Steady Decline in Testosterone
According to the meta-analysis Lawrence referenced, average testosterone levels in men have steadily decreased — by about 1% per year — since the 1970s. This isn’t just about aging. The drop is seen across all age groups.
Researchers suspect several culprits, including the steady increase in body fat levels, as men’s average BMI has risen significantly. Higher levels of body fat, particularly visceral fat, have been shown to negatively affect testosterone production.
And that’s not all. The researchers also suggest that changes in dietary fat intake may play a key role. Since the 1960s, the average percentage of calories coming from fat in the standard diet has fallen by roughly 10% — a downward trend fueled by the rise of low-fat dietary guidelines and processed food options.
The Meta-Analysis: Low-Fat vs. High-Fat Diets
The paper reviewed six clinical studies that directly compared low-fat diets (around 20% fat) and high-fat diets (around 40%).
Findings across studies included:
- A small to moderate decrease in total testosterone on lower-fat diets
- Reduction in free testosterone and dihydrotestosterone (DHT)
- No consistent change in sex hormone binding globulin (SHBG)
Why does SHBG matter? It binds to testosterone in the bloodstream, rendering it biologically inactive. So even if total testosterone is high, SHBG can prevent it from being usable. That makes tracking free testosterone — the accessible form — even more important.
Lawrence Tries the Diet Himself
With over a decade of self-tracking under his belt, Lawrence made an ideal study subject. Prior to this experiment, his macronutrient split was roughly:
- 30% fat
- 30% protein
- 40% carbohydrates
He boosted dietary fat intake to 40% for one month, adjusting carbohydrates downward to 30% to maintain the same calorie intake.
To mimic a prior blood test from three years earlier, he brought his body fat down to nearly identical levels (within 1.5 pounds of previous weight) and kept his protein intake steady. That way, any hormonal changes could be more confidently linked to fat intake rather than shifts in weight, body composition, or training.
Here’s What Changed
- Free testosterone increased slightly
- SHBG dropped from 98 nmol/L to 81 nmol/L (still high, but a noticeable drop)
- Total testosterone decreased a bit from earlier levels
This seems to contradict the meta-analysis, which found total T levels increased on a high-fat diet while SHBG remained stable. Lawrence believes his leaner physique, higher muscle mass, and specific fat sources may have influenced this different result.
Cholesterol: A Worthwhile Warning
One side effect Lawrence noticed was a rise in total cholesterol — higher than he’d ever seen before. However, not all markers were concerning:
- His LDL (“bad”) cholesterol was normal
- His HDL (“good”) cholesterol was very high, which helped inflate the total
- His non-HDL cholesterol remained within safe limits
This aligns with one study in the meta-analysis that observed an increase in cholesterol when participants shifted from low-fat to high-fat diets.
The Kind of Fat Matters
To avoid raising harmful cholesterol, Lawrence focused on healthier unsaturated fats including:
- Olive oil
- Avocados
- Peanut butter
- Fatty fish like salmon (2 servings/week)
- Fish oil supplements
- Eggs (up from 2 to 4 per day)
He specifically avoided excessive saturated fats, which are more strongly associated with negative impacts on heart health.
One study cited in the meta-analysis even found that simply swapping saturated fats for unsaturated fats increased testosterone by 17.4% to 19.9% — helping make the case for quality over quantity when it comes to dietary fats.
So, Should You Try a High-Fat Diet?
If you’re a man over 40 or 50 looking to nudge your testosterone upward, there are safer and potentially effective ways to experiment — but preparation is key.
Steps to Test This for Yourself:
- Track your current macros. Use a nutrition app to calculate what percentage of your calories come from fats now.
- Get blood work done first. You’ll want to know your baseline for total testosterone, free testosterone, SHBG, and cholesterol.
- Shift your fat intake to around 40% of your calories. Prioritize unsaturated fats and keep protein and carbs balanced.
- Stick with it for at least 4–6 weeks. That allows enough time for hormonal shifts to stabilize.
- Retest your blood levels. Compare results against your initial panel. Watch for changes in both testosterone and cholesterol.
Important caution: Lawrence strongly discourages going above 40% fat intake, since ultra-high fat diets can crowd out protein and carbs needed for energy, muscle preservation, and fiber intake — and may spike cholesterol unnecessarily.
The Bottom Line
While Lawrence’s personal results didn’t match the meta-analysis exactly, they support one enduring truth: hormones are deeply individual. What works for one man may not hold for another.
But one thing is clear — our diet choices matter. As men age, small adjustments to nutrition can potentially help preserve not only testosterone production but long-term health, energy, and quality of life.
Before trying any dietary overhaul, always consult with a healthcare provider and get comprehensive blood work done.
