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Last Updated: 12.06.23

Dr. Andy Galpin: How to Build Physical Endurance & Lose Fat

This is episode 3 of a 6‑part special series with Andy Galpin, PhD, professor of kinesiology at California State University, Fullerton. They explore endurance training, energy sources, fat loss, breathwork, lactate regulation, blood flow, and exercise combinations for improved performance.

Key Takeaways

High level takeaways from the episode.

Endurance comes down to two factors:

  • Fatigue management
  • Fueling

Quick way to improve endurance: improve mechanics and mechanical efficiency

  • Breathing techniques and patterns
  • Proper posture and positions
  • Movement technique

Train across the full spectrum of exercise, including steady-​​state and high-​​intensity interval training

Exercise snacks: short, intense bouts of exercise can improve cardiorespiratory fitness and cognitive benefits

  • Example: 20-​​second stair sprints repeated throughout the day
  • Studies show significant improvements in VO2 max and work productivity after incorporating exercise snacks into daily routines

Energy throughout the day is a form of endurance

  • Avoid lulls and fatigue, maintain focus and enjoyment in daily activities

Muscular endurance: repeat small efforts in a muscle group without fatigue

  • Example: walking up flights of stairs without quads burning

Maximum anaerobic capacity: perform a large amount of work for 20–80 seconds

  • Example: paddling hard for a minute while surfing or biking up a steep hill

Maximum aerobic capacity: repeat high-​​effort activities for 5–15 minutes

  • Example: running a mile or completing longer distance intervals

Sustained position: maintain posture and position for extended periods

  • Example: sitting with perfect posture at work, standing in line without collapsing

Endurance factors:

  • Sustained high-​​intensity exercise
  • Repeated high-​​intensity exercise
  • Long-​​duration low-​​intensity exercise
  • Maximum distance

Goal: Perform these activities and feel good afterwards

Endurance reflects fatigue management and energy production

Body has different fuel sources:

  • Glycogen (stored in muscle and liver)
  • Body fat (stored in white adipose tissue)
  • Protein
  • Phosphocreatine system

Body fat stores are tapped into when other fuel sources are depleted or when energy systems signal that body fat is the optimal fuel source

Fat loss occurs through respiration

  • Breathing in oxygen (O2) and exhaling carbon dioxide (CO2)
  • Carbon molecule difference between O2 and CO2
  • Carbohydrates and fats are chains of carbon
  • Metabolism breaks carbon bonds to produce energy and create ATP
  • Carbon must be removed from the body through respiration

Carbon is stored in the body as carbohydrates (liver, blood, muscles), fat (adipose tissue, intramuscular triglycerides), and protein (used for structure)

To lose weight, one must either ingest less carbon or expel more carbon

  • The type of exercise or diet does not matter as much as the total carbon intake and output

Steady-​​state exercise, weight lifting, and interval training all increase respiration rate and can lead to fat loss

Resting heart rate as a metric of fitness

  • Lower resting heart rate indicates better fitness
  • Sub-​​60 beats per minute is a good target for most people

Maximum heart rate not a good proxy for fitness

  • Does not increase with fitness

Training fasted does not necessarily enhance fat loss

Misconception: exercising in a “fat-​​burning zone” leads to more fat loss

  • Lower intensity exercise burns a higher percentage of fat, but total fuel expenditure is low
  • Higher intensity exercise burns a higher percentage of carbohydrates, but total fuel expenditure is higher

Burning fat does not equal losing fat from the body

Speed, power, and skill development have minimal benefit for fat loss

Strength training has some benefit, but total energy expenditure is low

Hypertrophy and muscular endurance training (6–30 repetitions) can help deplete muscle glycogen

High-​​intensity interval training can further deplete muscle glycogen and potentially liver glycogen

Glucose is the primary fuel source for the brain

Fatigue signals occur when muscle glycogen levels are lower than 75%

  • Most people quit around 50% depletion

Liver depletion leads to complete shutdown (e.g., marathon runners “bonking”)

  • Brain prioritizes self-​​preservation over pushing through fatigue

Fat cannot be turned into muscle, and muscle cannot be turned into fat

Burning muscle glycogen while in a hypocaloric state (below total caloric need) leads to fat loss

Metabolic flexibility: the ability to switch between using carbohydrates and fats for energy

Some markers to consider for metabolic flexibility:

  • Blood glucose levels 
    • Ideally around 85 mg/​​dL or lower
    • Every point increase above 85 increases the likelihood of developing type 2 diabetes by 6%
  • AST and ALT levels 
    • AST to ALT ratio around 0.8 or lower
    • Associated with blood glucose regulation
  • Performance tests
    • Standard workout with objective measures (time, heart rate, perceived exertion)

Metabolic flexibility is not always optimal for specific activities or sports

  • Glycolytically dominated sports may benefit from a bias towards carbohydrate utilization
  • Endurance sports may benefit from a bias towards fat utilization

Most people want to feel great throughout the day and be able to do various activities

  • Metabolic flexibility can help with this

Enhancing fat utilization:

  • Train in a pre-​​fat ingested state
  • Ingesting fat prior to training can signal the body to preferentially target fat as fuel
  • Be aware that relying on fat as fuel may hinder top-​​end performance

Enhancing carbohydrate utilization:

  • Train at a higher intensity
  • Ingest carbohydrates before exercise to bias towards carbohydrate utilization
  • Ensure protein and fiber intake is stable and combined with carbohydrate intake to
  • help stabilize blood glucose levels

Identifying poor fat utilization:

  • Difficulty performing fasted training
  • Slow heart rate recovery after exercise

Identifying poor carbohydrate utilization:

  • Crashing after consuming carbs
  • Slow to start during exercise

Oxygen is required for aerobic metabolism and waste management

Short Duration Exercise (Sprinting, 1 minute or less)

  • Primarily uses phosphocreatine and anaerobic glycolysis
  • Limited contribution from ingested carbohydrates, fats, or proteins

Medium Duration Exercise (3–5 minutes)

  • Transition from anaerobic glycolysis to aerobic metabolism
  • Increased reliance on ingested carbohydrates, fats, and proteins

Long Duration Exercise (20 minutes — marathon)

  • Predominantly aerobic metabolism
  • Increased reliance on fat stores and ingested fats for energy 
    • Be cautious of ingesting too many fast carbohydrates before exercise, as it can cause a blood sugar crash

Exercise has been shown to improve memory retention and exam scores

  • 20 minutes of exercise prior to taking an exam can lead to better performance
  • Lactate produced during exercise may contribute to these cognitive benefits

Low carbohydrate diets can be effective for weight management and energy stabilization

  • Not ideal for high-​​intensity or anaerobic exercise, as it downregulates enzymes responsible for using carbohydrates as a fuel source
  • Works well for people who do limited exercise or low-​​intensity, long-​​duration activities


Science-​​based tools and supplements that push the needle.

Exercise snacks for Cardiorespiratory Fitness and Cognition


Fat Loss Exercise Protocol



We recommend using this distillation as a supplemental resource to the source material.

  • Dr. Andy Galpin: How to Build Physical Endurance & Lose Fat

    Huberman Lab #112

    Episode 3: Andy Galpin, PhD, explores endurance training, energy sources, and fat loss for all fitness levels.

Full Notes

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