Updated 05/20/24 9:52 PM

Health and Performance:
Marathon Nutrition Plan: 30 years of success.

Caveats:

1. Do not change your nutrient intake within the month before a marathon.

2. This plan is not recommended for ultras.

How the Body Works (Physiology):

Although a few studies suggest carbohydrate loading is beneficial, many show no impact. Training increases the muscle storage capacity of glycogen and fat so training induced carbohydrate loading for months minimizes the benefits of carb loading a few days before a marathon. Since 3 grams of water are stored per gram of glycogen, athletes who carbohydrate load may gain 1-3 pounds in the final week. Training also increases mitochondrial number, size and efficiency which improves fat use by muscle.

At the start of a run, muscles use 50% carbohydrate (glucose) and 50% fat (fatty acids). Carbohydrates contain 4 calories/gram with 2000 calories stored as glycogen (400 in liver and 1600 in muscle). Since fat releases 9 calories/gram and more than 100,000 fat calories are stored in fat cells, muscles increase fat and reduce glycogen use during running. Glycogen depletion, chloride, potassium, lactate, leaky calcium channels, nerve exhaustion and other factors may contribute to muscle fatigue.

What reduces muscle glycogen depletion? Fasting.

During fasting, the liver releases glucose from glycogen but muscle glycogen is preserved. When liver glycogen is low, hormone sensitive lipase releases fat from fat tissue to be used as fuel. If you fast before running, you may use 70% fat and 30% glucose at the start and preserve muscle glycogen.

When you eat, insulin (the storage hormone) released from the pancreas allows carbohydrate (glucose), fat (fatty acids) and protein (amino acids) into cells to be used and stored. Insulin blocks the action of hormone sensitive lipase for up to 4 hours reducing fat release and use by muscle.

A comparison of fasted to non-fasted runners revealed increased fat mobilization, enhanced endurance performance and higher post run muscle glycogen in the fasted group. Pre-exercise feeding blunted metabolic signaling regulating fuel mobilization by reducing muscle release of anti-inflammatory interleukin 6.

Since digesting food can take up to 48 hours, a large meal the night before a marathon may be only partially digested at the start. Blood flow at rest: 20% muscle, 20% brain, 20% intestines, 20% kidney and 5% heart. Blood flow during exercise: 90% muscle, 5% heart, 3% brain, 1% intestines and 1% kidney. With reduced blood flow to the intestine during exercise, little digestion occurs and a large meal the night before increases the workload of running by adding weight. Many runners seeking help in the medical tent for nausea, abdominal pain, diarrhea or vomiting report eating before or during the marathon.

Based on this physiology, I have trained athletes to reach peak organ function for 30 years through Organs R Us (ORU), a volunteer non-profit promoting organ donation and healthy organs through exercise and nutrition. One ORU runner completed 7 marathons on 7 continents.

Day Prior: Eat a small lunch. Skip dinner or eat light (fluids, soup).

SFM Morning: Drink non-calorie fluids. Avoid carbohydrate, fat and protein which raises insulin for up to 4 hours and blocks the lipase enzyme releasing fat, the best muscle fuel.

During SFM: Drink non-calorie fluids. Remember calories increase insulin. Exercise increases norepinephrine and epinephrine (plus glucagon, thyroid hormone, cortisol and others) helping to shunt blood from intestine to muscle and skin. Eating increases intestinal activity diverting blood from muscle and sends conflicting messages (rest and digest vs fight or flight). Many elite runners drink fluids, commonly tea, before running.

Nothing feels as good as running empty.

We're excited to re-introduce Dr. Jeff Shapiro to our SFM community. If you're looking to improve your health and performance, you know an overwhelming amount of information and opinion is conflicting, counterproductive or harmful.

We're giving Dr. Jeff a platform to address this.

In his articles, Dr. Jeff will discuss exercise and nutrition physiology (how the body works) allowing you to ignore chatter and reject myths. For example, should you carbohydrate load and/or eat during running? Are pills on SFM weekend harmful? After graduating from Stanford and Yale, Dr. Jeff served as medical director of the San Francisco Marathon for a decade, completed and lectured at 50 marathons and trained athletes to achieve peak organ function for 30 years.

Dr. Jeff appeared on ABC News' 20/20 "Super Humans," consulted for CBS News' 60 Minutes "The Toughest Race" and co-produced “Ultra Running” for The Late Show. At the 2023 San Francisco Marathon, Dr. Jeff received a standing ovation for his presentation on exercise/nutrition physiology and adverse effects of pills.

Since he teaches physiology, Dr Jeff’s presentations will read like science instead of a blog. Train Well with Dr Jeff starting in May 2024.