The carbohydrate targets in this planner reflect the mainstream endurance nutrition consensus -- high carbohydrate availability for sustained performance in events over 90 minutes. This is well-supported by the work of Jeukendrup, Burke, Hawley, and others, and represents how most competitive Ironman athletes fuel today.

It is not the only approach. In a debate published in the American Journal of Clinical Nutrition in May 2026, Dr. Louise Burke and Dr. Timothy Noakes -- two of the most influential researchers in endurance nutrition -- presented opposing views on whether a low-carbohydrate, high-fat diet impedes performance. Burke's position: fat requires more oxygen than carbohydrate to produce the same energy, and this oxygen cost matters at race intensity. Noakes' position: after four to six weeks of adaptation, athletes perform similarly on both diets, and blood glucose maintenance -- not glycogen depletion -- may be the primary performance limiter in long events. Both positions are evidence-based. Neither is settled.

What this means for you. The targets this tool generates are a starting point grounded in one well-supported model. Your individual response depends on your metabolic history, training approach, GI tolerance, health goals, and how well you have practiced your nutrition. An athlete who has trained fat-adapted for years may not need or tolerate the carbohydrate levels shown here. An athlete with a history of GI distress at high CHO intake needs a different approach than the numbers suggest. Use this tool to build a plan, then refine it with your coach based on what your body actually does. Book a free BPC consult →