By James Frost, Founder of Flaming Phoenix. Phoenix Bars have been carried to the summit of Everest and used on expeditions from the Sahara to the Arctic.

Last updated: May 2026

What this guide covers

Ultra-high-carb solid foods are the calorie-dense, carbohydrate-rich solid fuels that endurance athletes rely on when gels and sports drinks stop working. For efforts longer than six hours (ultra runs, Ironman, mountaineering, multi-day expeditions, ocean rowing, audax cycling), solid food is not a backup option, it is the primary fuel that lets you finish.

This guide explains the science of why solids win past hour 6, lists the highest-carb solid foods that actually work mid-effort, and shows how to hit the 90g per hour carb target without relying on gels alone.

Key points: most ultra athletes under-fuel because of flavour fatigue from sweet gels, not because they don't know they need calories. Solid foods solve flavour fatigue, deliver psychological satiety, and reduce GI distress over multi-hour efforts. The trade-off is slower gastric emptying, so timing matters. Phoenix Bars deliver 66g of carbohydrates and 557 calories per 120g bar, the highest carb load I've seen in any portable solid food on the market.

Why solid carbs win past hour six

For efforts longer than six hours, solid food outperforms gels and drinks for three reasons: flavour tolerance, gut comfort, and psychological satiety.

The science is settled on the carbs themselves. Whether the source is liquid, gel, or solid, oxidation rates are roughly equivalent at moderate intensity. The 2019 University of Illinois study comparing potato purée, gels, and water during prolonged cycling found no performance difference. What changes over hours is what the gut and brain will accept.

Three things break down on long efforts. First, flavour fatigue: sweet liquid carbs become intolerable after 4 to 6 hours, and athletes stop eating not because they aren't hungry but because they cannot stomach another gel. This is the single biggest cause of ultra-distance bonking. Second, GI distress from concentrated sugars: sustained intake of high-osmolality liquid carbs damages the gut lining over multi-hour windows, and solid foods buffer the carb load. Third, psychological under-fuelling: the act of chewing real food signals satiety in a way liquid does not, and athletes consistently report eating more total calories when solids are part of the strategy.

The 2021 Japanese study of a female athlete completing a 438km mountain ultramarathon found that solid food intake correlated directly with faster running pace compared to liquid and gel sources, across 155 hours of continuous effort.

For efforts under 3 hours, gels and drinks are usually the right tool. This guide is not anti-gel. It is for the window where gels stop working, which is roughly hour 6 onwards.

The 90g per hour carb target

Current sports nutrition consensus puts ultra-endurance carb targets at 90 to 120g per hour, achieved through multiple-transportable carbohydrates (glucose plus fructose at a roughly 2:1 ratio). At this intake level, glucose uses the SGLT1 transporter (which saturates at 60g/hr) and fructose uses GLUT5, allowing total absorption above the single-source ceiling.

Hitting 90g/hr from solids alone requires careful food selection. Most commercial energy bars deliver 20 to 40g of carbs per serving, so to hit 90g/hr you'd need 2 to 4 bars per hour, which is impractical and expensive.

A Phoenix Bar delivers 66g of carbohydrates and 557 calories per 120g bar. One bar covers approximately 44 minutes at the 90g/hr target, or just over an hour at the 60g/hr target most ultra runners realistically achieve. For full coverage of how Phoenix Bars are used in ultras, see the Ultra-Endurance and Expedition Nutrition Guide.

What makes a solid food work mid-effort

Five attributes separate solid foods that work from solid foods that fail during sustained exercise.

High carb-to-fat ratio. Fat slows gastric emptying. High-carb solids empty the stomach faster and deliver fuel sooner.

Low fibre. Fibre is essential for everyday health but causes GI distress under exercise stress. Race-day solids should be low-fibre.

Soft texture, easy to chew. When you're exhausted, oxygen-deprived, or wearing gloves, dense or hard foods don't get eaten.

Heat and cold stable. Solids must not melt in summer heat or freeze in winter cold. This rules out chocolate-coated bars and fresh fruit.

Compact and packable. Calorie density per gram matters when you're carrying everything on your back. More on this in Calorie-Dense Foods.

High carb solid foods that work, ranked

The list below covers solid foods that consistently work for endurance athletes during efforts over 3 hours. Carb content per typical serving in brackets.

Tier 1, race-day solids (low fibre, fast emptying): Phoenix Bars (66g carbs, 557 cal per 120g bar), white rice cakes with jam (40g per cake), boiled new potatoes with salt (30g per 100g), maple syrup waffles or Stroopwafel-style biscuits (20g per waffle), Medjool dates (18g per date), ripe banana (27g per medium fruit).

Tier 2, multi-day expedition solids (slightly higher fat for satiety, still carb-led): Phoenix Bars (used as both race fuel and meal replacement, see How To Use Phoenix Bars), flapjacks made with rolled oats and golden syrup (50 to 70g per piece, varies), malt loaf (30g per slice), tortillas with honey or jam (30g per filled tortilla), fig rolls (15g per biscuit), boiled rice balls or onigiri (40g per rice ball).

Tier 3, recovery and base camp solids: pasta with white sauce (60 to 80g per portion), porridge with banana and honey (50 to 70g per bowl, see High Calorie Porridge), white bread sandwiches with jam (45g per sandwich).