Addendum: A Few Important Corrections
- Calories still determine the long-term scoreboard.
- Hormones influence when fuel is stored, released, and burned.
- But long-term fat gain or loss still requires a net energy surplus or deficit.
- Fat release is not the same as fat loss.
- Lipolysis = fat is released from the fat cell.
- Fat oxidation = that fat is actually burned for energy.
- Fat loss = over time, more fat leaves storage than returns to it.
- Released fatty acids can be re-stored, so activating HSL does not automatically mean losing body fat.
- HSL is not the only fat-release enzyme.
- ATGL begins triglyceride breakdown.
- HSL continues it.
- MGL completes it.
- Think of them as the offensive line for fat mobilization, rather than HSL acting alone.
- Insulin remains a major brake on lipolysis.
- Higher insulin strongly suppresses release of stored fat.
- Lower insulin makes fat mobilization easier.
- But this does not mean lower insulin automatically produces greater net fat loss.
- Low-carb diets increase fat burning, but fat burning ≠ fat loss.
- Lower carbohydrates generally mean lower insulin and higher fat oxidation.
- However, if you are also eating more fat, some of that burned fat may simply be dietary fat.
- The important question remains: is stored body fat decreasing over time?
- My original equation
Δ Fat = C × (Calories In − Calories Out)
was too simplistic.- There is no useful constant C that simply falls when carbohydrate intake falls.
- Macronutrients affect satiety, thermic effect, hormones, substrate use, and behavior, but they do not create a simple carb multiplier.
Exercise Is Even More Interesting Than I Originally Thought
- Muscle contraction can activate GLUT4 without insulin.
- Exercise gives muscle a second key to the glucose door.
- This temporarily bypasses part of the problem of insulin resistance.
- Exercise also:
- increases GLUT4 expression
- activates AMPK
- increases energy demand
- improves subsequent insulin sensitivity
- helps preserve/build muscle mass
- My statement that exercise is the ONLY way to improve insulin sensitivity was wrong.
- Weight loss, calorie restriction, sleep, medications, and other interventions can also improve insulin sensitivity.
- Exercise is special because it can increase glucose uptake independently of insulin while also improving later insulin response.
Insulin Resistance Is More Complicated
- I originally imagined insulin resistance as:
- insulin yelling louder
- cells ignoring it
- fat becoming permanently locked away
- That is incomplete.
- In adipose insulin resistance, fat cells can also become resistant to insulin’s ability to suppress lipolysis.
- That can mean too much fatty acid release at the wrong time.
- Those fatty acids can then accumulate in places like the liver and muscle.
- So insulin resistance can involve both:
- high insulin
- and poor control over fat release
Add Ghrelin: The Hunger Signal
- Ghrelin belongs in the game, but not directly on Team Storage or Team Liberation.
- Ghrelin is closer to:
- “We need more fuel. Go find food.”
- Ghrelin generally:
- rises during fasting
- increases hunger
- increases food-seeking/reward
- falls after eating
- stimulates growth hormone
- This creates an interesting situation during fasting:
- Insulin falls
- fat mobilization rises
- ghrelin rises
- therefore the body is simultaneously saying:
- “Use stored energy.”
- and “Please go acquire more energy.”
The Updated NFL Model
- Scoreboard: long-term energy balance
- Insulin: favors storage and suppresses fat withdrawal
- Catecholamines: encourage fuel mobilization
- Ghrelin: tells you to go acquire more fuel
- Leptin: signals longer-term energy reserves
- GLP-1 / PYY / CCK: help signal that food has arrived
- ATGL / HSL / MGL: execute fat mobilization
- GLUT4: moves glucose into cells
- Muscle: a huge metabolic sink for glucose and energy
- Exercise: changes both the immediate play and how well the team performs afterward
The cleanest way I now think about the whole system is:
Calories determine the long-term scoreboard. Hormones determine how the game is played.
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