Carbohydrates, Starches & Legumes
The misunderstood macronutrient that fuels champions
The Big Picture
Carbs have been demonized for decades. "Carbs make you fat." "Go low-carb for performance." "Bread is the enemy."
Here's what the science actually shows: carbohydrates are the preferred fuel for high-intensity athletic performance. When you sprint, lift heavy, or compete at high intensity, your body runs on glucose—which comes from carbs.
The real question isn't "carbs or no carbs." It's which carbs, when, and how much.
What Are Carbohydrates?
Carbohydrates are molecules made of carbon, hydrogen, and oxygen. Your body breaks them down into glucose—the fuel your cells use for energy.
The Three Types
| Type | What It Is | Examples | Speed of Absorption |
|---|---|---|---|
| Simple Sugars | 1-2 sugar molecules | Table sugar, fruit, honey | Fast (minutes) |
| Complex Starches | Long chains of sugar | Bread, rice, potatoes | Moderate (1-2 hours) |
| Fiber | Indigestible plant material | Vegetables, beans, whole grains | Not absorbed (feeds gut bacteria) |
The key insight: not all carbs behave the same in your body. A sweet potato and a candy bar are both "carbs," but they have completely different effects.
What ISP Students Learn
Lesson 1: The Glycemic Response—Why Processing Matters
When you eat carbs, your blood sugar rises. How fast and how high it rises determines:
- How much insulin your body releases
- Whether you get sustained energy or a crash
- Whether excess glucose gets stored as fat
The Food Matrix Effect:
| Food | Form | Glycemic Impact |
|---|---|---|
| Whole apple | Intact | Slow, moderate rise |
| Apple juice | Liquid, no fiber | Fast, high spike |
| Apple sauce | Pureed, some fiber | Medium |
The fiber, water, and cell walls in whole foods slow digestion. When you remove them (by juicing, refining, or processing), the sugar hits your bloodstream faster.
What this means for athletes: Whole food carbs give sustained energy. Processed carbs give quick spikes followed by crashes.
Lesson 2: Resistant Starch—The Carb That Acts Like Fiber
Not all starch gets digested in your small intestine. "Resistant starch" passes through to your colon, where it feeds beneficial bacteria.
How to increase resistant starch:
| Method | What Happens | Examples |
|---|---|---|
| Cook and cool | Starch "retrogrades" into resistant form | Cold potato salad, overnight oats, day-old rice |
| Eat less ripe | Unripe = more resistant starch | Green bananas, firm bananas |
| Choose high-RS foods | Naturally high in resistant starch | Beans, lentils, oats |
The benefits:
- Feeds good gut bacteria
- Produces short-chain fatty acids (anti-inflammatory)
- Improves insulin sensitivity
- Increases satiety
What this means for athletes: Meal prep works in your favor. That rice you cooked yesterday is actually healthier today.
Lesson 3: Legumes—The Longevity Food
Beans, lentils, chickpeas, and peas are the single food group most consistently associated with long life across all studied populations.
Why legumes are special:
| Benefit | How It Works |
|---|---|
| Blood sugar stability | High fiber + protein slows absorption |
| "Second meal effect" | Eating beans at lunch improves blood sugar at dinner |
| Gut health | Prebiotic fiber feeds beneficial bacteria |
| Complete nutrition | Protein, fiber, minerals, B vitamins in one package |
The Blue Zones connection: In every "Blue Zone" (regions where people live longest), beans are a daily staple—not occasional.
What this means for athletes: Beans aren't just "peasant food." They're performance food that supports recovery, gut health, and long-term health.
Lesson 4: Carb Periodization—Match Fuel to Training
Elite sports nutritionists don't prescribe the same carb intake every day. They periodize:
| Training Type | Carb Recommendation | Why |
|---|---|---|
| High-intensity / competition | High carbs (6-10g/kg body weight) | Muscles need glycogen for power |
| Moderate training | Moderate carbs (4-6g/kg) | Replenish without excess |
| Rest / low-intensity | Lower carbs (3-4g/kg) | Less fuel needed, promote fat adaptation |
This isn't "low-carb" ideology—it's matching fuel to demand.
What this means for athletes: Don't eat the same amount of carbs every day. Eat more on hard training days, less on rest days.
The Best Carb Sources
Tier 1: Eat Daily
- Beans and lentils — Fiber, protein, resistant starch
- Whole grains — Oats, quinoa, brown rice, whole wheat
- Starchy vegetables — Sweet potatoes, squash, corn
Tier 2: Eat Regularly
- Whole fruits — Natural sugars with fiber and vitamins
- Root vegetables — Carrots, beets, parsnips
Tier 3: Use Strategically (Around Training)
- White rice — Fast-digesting, good post-workout
- Bread — Choose whole grain when possible
- Sports drinks — Only during prolonged, intense exercise
Minimize
- Refined grains — White bread, pastries, most crackers
- Added sugars — Candy, soda, most desserts
- Fruit juice — Sugar without fiber
Key Takeaways
| Lesson | One-Liner |
|---|---|
| Processing matters | Whole food carbs beat refined carbs every time |
| Resistant starch | Cook, cool, and reheat starchy foods for extra benefits |
| Legumes daily | Beans are the most consistently linked food to longevity |
| Periodize carbs | Match your carb intake to your training demands |
How This Shows Up at ISP
Carbohydrate science informs the Bio Skill Tree in MyPath:
- Fueling Consistency tracks carb timing around training
- The "Legume Week" challenge introduces beans into daily eating
- Gut Health emphasizes resistant starch and fiber diversity
- Recovery Protocol teaches post-workout carb strategies
When ISP students plan their nutrition, they're not afraid of carbs—they understand when and how to use them.
Common Questions
"Don't carbs make you fat?"
Excess calories make you fat, regardless of source. Whole food carbs are actually hard to overeat because fiber makes you full. Processed carbs are easy to overeat because they lack fiber.
"Should athletes go low-carb?"
For most athletes, no. Low-carb diets impair high-intensity performance. They may work for ultra-endurance or rest periods, but most athletes need carbs for power and recovery.
"Are beans really that important?"
The research is remarkably consistent: populations that eat beans daily live longer and have lower rates of chronic disease. It's one of the most robust findings in nutrition.
Learn More
"Carbs aren't the enemy. Processed carbs eaten at the wrong time are the enemy. Whole food carbs matched to your training are rocket fuel."