New Study Questions Ketone Ester Benefits for Cyclists

Ketone ester supplements have been quietly spreading through the pro peloton since 2019, with teams reportedly spending $500-1,000 per rider per month on the bitter-tasting drinks. But a new study published in Medicine & Science in Sports & Exercise casts serious doubt on whether these expensive supplements actually improve cycling performance for efforts lasting less than two hours—the duration of most road races, crits, and criteriums.

Researchers at Australian Catholic University tested 32 trained cyclists (average VO2max 62 ml/kg/min, FTP 310 watts) across three conditions: ketone ester supplementation, carbohydrate-matched placebo, and control. After consuming the supplements, riders completed a 90-minute steady-state ride at 65% FTP followed by a 15-minute maximal time trial. The result? No significant difference in time trial power output, completion time, or perceived exertion between groups. Average power across all three conditions hovered within 2-3 watts—well within normal testing variability.

The Biochemistry Behind the Hype

Ketone esters elevate blood ketone concentrations to 2-4 millimolar (mmol/L), similar to levels achieved after 2-3 days of fasting or strict ketogenic dieting. The theory holds that ketones provide an alternative fuel source to glucose and fat, potentially sparing muscle glycogen and delaying fatigue during prolonged efforts. Some research suggests ketones may also reduce lactate accumulation and improve oxygen utilization efficiency.

The challenge lies in timing and context. Earlier studies showing modest performance benefits—typically 1-3% improvements in time to exhaustion—involved ultra-endurance efforts lasting 3+ hours where glycogen depletion becomes a limiting factor. In those scenarios, any additional fuel source could theoretically help. But for efforts under two hours where trained cyclists have adequate glycogen stores and can consume sufficient carbohydrates during exercise, the metabolic advantage disappears.

The Australian study measured blood ketone levels at 3.2 mmol/L thirty minutes post-ingestion, confirming the supplements worked as intended. Yet despite elevated ketones circulating through the bloodstream, power meter data showed no meaningful difference. Muscle biopsy analysis revealed no significant differences in glycogen utilization rates between groups, suggesting ketones didn't spare carbohydrate stores as hypothesized.

Why the Pro Peloton Still Uses Them

If the science doesn't support performance benefits for typical race durations, why are WorldTour teams investing six figures annually in ketone supplements? Several factors may explain the disconnect.

First, professional stage racing involves multi-day efforts where cumulative fatigue and glycogen management matter more than single-day performance. A 1-2% improvement in recovery between stages could theoretically compound over three weeks, though no long-term studies have confirmed this. Second, placebo effects in professional sports are powerful—if riders believe a supplement helps, that confidence may translate into improved performance regardless of biochemical reality.

Third, marginal gains culture encourages trying everything that might work, even if evidence remains mixed. When the difference between podium and pack can come down to a handful of watts over the final climb, teams are willing to experiment with supplements that show even equivocal results in research settings.

It's also worth noting that ketone ester formulations vary. The Australian study used a specific ester compound at 25 grams per serving, while commercial products range from 10-30 grams per dose with different molecular structures. Some formulations may prove more effective than others, though head-to-head comparisons are scarce.

Practical Considerations and Side Effects

Ketone esters taste notoriously bad—users describe flavors ranging from nail polish remover to industrial solvent—and gastrointestinal distress affects roughly 30% of users, especially at higher doses. Nausea, cramping, and diarrhea mid-race would negate any theoretical performance benefit, making individual tolerance testing crucial before competition use.

Cost remains prohibitive for most cyclists. Retail prices for ketone ester supplements range from $30-50 per serving, compared to $2-3 for equivalent carbohydrate-based sports nutrition. If you're racing or training 4-5 times per week, that's $600-1,000 monthly—approaching the cost of a power meter or quality wheelset that would deliver measurable, proven performance improvements.

From a regulatory standpoint, ketone esters occupy a gray area. They're not banned by WADA or UCI, but they're also not classified as food or dietary supplements in many jurisdictions. Quality control and contamination risk vary by manufacturer, potentially exposing athletes to inadvertent doping violations if products contain unlisted ingredients.

Alternative Strategies for the Same Goals

If the goal is improving fat oxidation efficiency and sparing glycogen, periodized carbohydrate availability training offers a proven, free alternative. Training sessions performed in a fasted state or with depleted glycogen stores force metabolic adaptations that improve fat burning capacity. Research shows 8-12 weeks of strategically timed low-carb training sessions can increase fat oxidation rates by 15-25% without requiring supplements.

For recovery between hard efforts, high-quality carbohydrate and protein intake within 30-60 minutes post-exercise remains the gold standard. A 3:1 or 4:1 carb-to-protein ratio (30-50g carbs, 10-15g protein) replenishes glycogen and initiates muscle repair for pennies per serving compared to ketone esters.

What This Means for Your Riding

Unless you're competing in ultra-endurance events lasting 4+ hours where glycogen depletion becomes inevitable—think 200-mile gran fondos, double centuries, or gravel races exceeding six hours—ketone esters offer questionable return on investment. The latest research suggests you'll get better performance and financial value from optimizing basic sports nutrition: adequate carbohydrate intake during exercise (60-90 grams per hour for efforts over 90 minutes), proper hydration, and structured recovery nutrition.

If you're curious about metabolic flexibility and fat adaptation, work with a qualified sports dietitian to implement periodized nutrition strategies that align with your training phases. These evidence-based approaches deliver measurable results without the cost, taste, or GI side effects of ketone supplementation.

The cycling industry regularly cycles through supplement trends—remember the beetroot juice boom of 2015, or sodium bicarbonate loading before that? While some supplements eventually prove their worth through rigorous research, others fade as initial hype meets scientific scrutiny. Based on current evidence for typical cycling efforts, ketone esters appear to fall into the latter category—an expensive experiment that may work for specific ultra-endurance contexts but offers little benefit for the riding most of us actually do.