Burn Fat Longer, Bonk Later — UCLA Moved the Metabolic Threshold 10.5%

Key Takeaways

• A double-blind UCLA trial showed 10.5% improvement in metabolic threshold after 12 weeks (p<0.02) — meaning you can work 10.5% harder before lactate overwhelms your system.
• Ventilatory threshold also increased by 8.5% — the point where your breathing goes from controlled to desperate moved to a higher intensity.
• VO2 max did not change, which means Cordyceps got more out of the same engine — greater aerobic efficiency, not just a bigger ceiling.
• A higher metabolic threshold means more fat burning at higher intensities — and more glycogen spared for when you truly need it.

Why This Matters for You

Races are not won at VO2 max. They are won at threshold — the pace you can sustain for the duration. If your metabolic threshold moves by 10.5%, a 7:30 per mile threshold pace becomes 6:47. A 200-watt cycling threshold becomes 221 watts. You are not just fitter — you are training and racing in a more efficient zone, burning fat longer, accumulating lactate slower, and holding it together when everyone else is fading. This study used older subjects, but the mechanism — AMPK activation, mitochondrial efficiency, lactate clearance — is age-independent.

Every endurance athlete has a number that matters more than their finish time, more than their training pace, more than their VO2 max. It is the intensity at which their body shifts from burning fat efficiently to burning glycogen desperately. It is the line between sustainable and unsustainable. Cross it too early, and you bonk. Stay below it, and you can go all day.

It is called the metabolic threshold, and a team at UCLA demonstrated that Cordyceps can raise it by 10.5%.

The UCLA Study

In 2010, Steve Chen, Zhaoping Li, and colleagues at UCLA's Center for Human Nutrition published a double-blind, placebo-controlled, prospective trial examining the effects of Cs-4 (a standardized Cordyceps sinensis extract) on exercise performance.

Twenty healthy subjects, ages 50 to 75, were randomized to receive either Cs-4 at 333mg three times daily (approximately 999mg/day total) or placebo for 12 weeks. Exercise testing used breath-by-breath gas analysis on a cycle ergometer -- real-time measurement of every breath, calculating exact oxygen consumption and CO2 production at each intensity level.

The Two Thresholds

The metabolic threshold is the intensity at which lactate production outpaces clearance. Below it, your body burns fat and glucose aerobically with minimal lactate. Above it, anaerobic metabolism accelerates, lactate accumulates, and glycogen depletes rapidly.

The ventilatory threshold is where breathing rate spikes disproportionately to workload -- the point where you go from "I can talk" to "I cannot speak," as the body tries to blow off excess CO2 from buffering lactate.

Both typically occur at 60-85% of VO2 max. Raising them means working harder while staying in the efficient zone.

The Results

After 12 weeks, the Cordyceps group showed:

Metabolic threshold: +10.5%, increasing from 0.83 +/- 0.06 L/min to 0.93 +/- 0.08 L/min (p<0.02). The placebo group showed no significant change.

Ventilatory threshold: +8.5%, increasing from 1.25 +/- 0.11 L/min to 1.36 +/- 0.15 L/min. The placebo group showed no significant change.

The p-value of less than 0.02 for the metabolic threshold means there is less than a 2% probability that this result occurred by chance. In exercise physiology, where biological variability is high, this is a strong result.

Interestingly, VO2 max did not change in either group. This is not a contradiction -- it is an important distinction. The threshold shifts tell us that Cordyceps improved the efficiency of the aerobic system within its existing ceiling. The participants could do more work aerobically without necessarily having a higher maximal capacity.

What 10.5% Looks Like in Practice

For a runner whose metabolic threshold corresponds to a 7:30 per mile pace, a 10.5% improvement moves that threshold to approximately a 6:47 pace. That means they can hold a faster pace while still in fat-burning, lactate-clearing, sustainable mode. Their "easy hard" pace becomes significantly faster.

For a cyclist, if the metabolic threshold occurs at 200 watts, a 10.5% increase pushes it to 221 watts. That is 21 more watts of sustainable power output -- the kind of difference that changes race strategy and opens up new performance tiers.

For a CrossFit athlete or functional fitness competitor, a higher metabolic threshold means more work done aerobically during metcons. Less gasping. More composure. Better pacing. Cleaner movement in the later rounds when everyone else is breaking down.

The Fat-Burning Implication

Below the metabolic threshold, the body preferentially burns fat as fuel. Above it, glycogen becomes the primary source -- and glycogen is limited (roughly 2,000 calories stored versus 50,000+ calories of fat in a lean athlete).

A higher metabolic threshold means the body stays in fat-burning mode at higher intensities. For ultra-endurance athletes, this is the difference between bonking at mile 20 and bonking at mile 23. More energy from fat means more glycogen preserved for when you truly need it.

For athletes optimizing body composition, it means harder training sessions that still draw primarily from fat stores rather than depleting glycogen and triggering the hunger cascade that follows.

Limitations and Context

The participants were 50-75 years old. Does this apply to younger athletes? The underlying mechanisms -- AMPK activation, mitochondrial efficiency, lactate clearance -- are age-independent. The magnitude of improvement may differ in younger, fitter populations, but the direction is consistent with the Hirsch 2016 findings in adults averaging 22.7 years.

The dose was approximately 1 gram per day, higher than a single capsule but achievable with consistent daily use. The study reported no evidence of hepatotoxicity -- liver function markers were normal throughout.

Why Thresholds Matter More Than Max

Most athletes never compete at VO2 max. Races are won and lost at threshold -- the sustainable intensity maintained for the duration of an event. Two athletes with identical VO2 max values can have dramatically different performance levels based on where their thresholds sit. Cordyceps, based on this data, raises the threshold without necessarily changing the ceiling -- getting more out of the aerobic engine you already have.

Source: Chen S, Li Z, Krochmal R, Abrazado M, Kim W, Cooper CB. "Effect of Cs-4 (Cordyceps sinensis) on Exercise Performance in Healthy Older Subjects: A Double-Blind, Placebo-Controlled Trial." Journal of Alternative and Complementary Medicine, 2010. [Read on PubMed Central](https://pmc.ncbi.nlm.nih.gov/articles/PMC3110835/) | [Read on PubMed](https://pubmed.ncbi.nlm.nih.gov/20804368/)