Food As Fuel

Overview

This chapter breaks down how the three macronutrients-carbohydrates, proteins, and fats-support exercise performance at distinct timepoints: before, during, and after workouts. You’ll learn the physiological role each macronutrient plays in energy production and recovery, practical serving targets tied to workout timing, and simple signals to monitor this week that show whether your fueling is working.

Who this is for: active people who train 3-6 times per week and want clear, evidence-based feeding targets to improve training quality, reduce post-workout soreness, and speed recovery.

Key benefits:

• Better quality workouts from improved pre-exercise energy.
• Faster recovery and less muscle breakdown after lifting or intervals.
• Simple, measurable rules you can test this week (e.g., grams of carbs pre-workout, protein within 30-90 minutes post-workout).

Health Foundations

Exercise stress demands fuel and building blocks. The body uses different pathways depending on intensity and substrate availability. Here are the core mechanisms in plain language:

• Glycogen (stored carbohydrate) is the primary fuel for moderate-to-high intensity efforts. When you sprint or lift heavy, anaerobic glycolysis provides rapid ATP but consumes glycogen quickly. Depleted glycogen reduces power output and increases perceived effort.
• Fat oxidation covers most low-intensity, long-duration work. It’s efficient but slower; it cannot meet sudden high-power demands. Training can increase mitochondrial density and fat use, but carbohydrate remains critical for high-intensity sessions.
• Protein supplies amino acids for repair and adaptation. Resistance training triggers muscle protein synthesis (MPS); adequate leucine-rich protein and total calories are necessary to net positive muscle remodeling.
• Hormones like insulin and cortisol mediate fuel partitioning: insulin promotes nutrient uptake (helps refill glycogen and build muscle), while elevated cortisol with inadequate carbs/protein can increase muscle breakdown.
• Risk factors for poor performance and recovery include chronically low carbohydrate intake around workouts, inadequate daily protein (below ~1.2 g/kg for most active people), and insufficient overall energy intake leading to negative energy balance and impaired recovery.

Specific example: A 75 kg cyclist doing 90-minute intervals will deplete ~300-400 g of glycogen over several hard sessions per week unless carbohydrates are prioritized around training and on recovery days.

Practical Protocol

This protocol gives concrete numbers and timing you can test over the next 7 days. Adjust for body size, training duration, and goals.

1. Pre-workout (30-90 minutes before)

• Aim for 0.4-1.0 g/kg of carbohydrates depending on session length/intensity.
• Example: 75 kg lifter → 30-75 g carbs (e.g., banana + 250 mL sports drink = ~45 g).
• Include 10-20 g protein if training fasted or if session is >60 min (helps blunt muscle breakdown).

2. During workout (for sessions >60-90 min or repeated high-intensity efforts)

• Consume 30-60 g carbs/hour for endurance-style or multi-hour sessions.
• For sessions under 60 minutes, water only is often sufficient unless glycogen was low pre-workout.
• Use easily digestible sources (glucose/maltodextrin sports drinks, gels, or bananas).

3. Post-workout (within 30-90 minutes)

• Prioritize 0.3-0.5 g/kg protein to stimulate MPS, with at least 2.5-3 g leucine when possible.
• Example: 75 kg → 22-38 g protein (chicken, whey shake, or Greek yogurt).
• Add 0.5-1.2 g/kg carbohydrates depending on how depleted you are and time until next session.
• If training again within 24 hours or did long intervals: aim for the higher end.

Progression milestones (4-week test):

• Week 1: Implement pre- and post-workout targets on three main sessions.
• Week 2: Add intra-workout carbs for sessions >60 min.
• Week 3-4: Track perceived exertion and time-to-exhaustion improvements; increase carbs modestly if heavy sessions feel worse.

Safety/warning signs - see a healthcare professional if:

• You experience recurrent lightheadedness, syncope, or arrhythmias during exercise.
• You develop unexplained weight loss, persistent fatigue, or inability to complete usual workouts despite following fuel targets (could indicate inadequate overall energy, endocrine issues, or overtraining).
• New gastrointestinal symptoms when trying intra-workout feeds (may need GI evaluation or progressive gut-training).

Comparison for quick clarity:

• Short, high-intensity session (90 min): pre 0.8-1.0 g/kg carbs; intra 30-60 g/hr; post 0.3-0.5 g/kg protein + 1.0-1.2 g/kg carbs.

Tool suggestion: Use a kitchen scale and a simple app (e.g., Cronometer) for one week to track grams/kg for carbs and protein and compare against the targets above.

Common Mistakes

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