Insulin
Hormone Glucose Transport Nutrient Partitioning
Insulin is a peptide hormone secreted by the pancreas. It lowers blood glucose by promoting uptake into muscle and fat cells while storing glycogen in liver and muscle. In muscle-building contexts, insulin supports MPS and recovery when paired with sufficient protein and training. Its effect is systemic – part of the network of training, energy availability, sleep and stress management, not a standalone switch.
Definition and System Context
Briefly Explained Insulin enables glucose uptake, replenishes glycogen and modulates nutrient flow. In strength training it works synergistically with amino acids: protein triggers MPS, insulin facilitates nutrient transport and suppresses excessive MPB. Progress depends on systemic control: training within MEV and MRV, guided by RIR and RPE, with consistent sleep and energy intake.
- Signal, not a villain: Insulin itself doesn’t cause fat gain – energy balance (maintenance calories) drives outcomes.
- Timing in context: Around training, carbs can accelerate glycogen replenishment and maintain session quality – within your TDEE and goals.
- Hardgainer insight: High NEAT plus low intake slows progress – no “insulin fear” required.
Measurement & Application
Insulin levels themselves are rarely a useful standalone metric. More practical are trends in fasting glucose, energy, performance and recovery. Function matters more than single readings without context.
- Glycogen & Performance: Adequate carbohydrates sustain training quality; depleted stores blunt SRA-aligned progression.
- Protein Synergy: Ensure sufficient protein per meal; hit the leucine threshold.
- Track trends: Bodyweight, steps (NEAT), sleep and performance over time reveal the bigger picture.
Guidelines for Growth (Guardrails)
- Energy Availability: Define a lean surplus; fine-tune using Rate of Gain.
- Carb Placement: Carbs pre/post training enhance performance and recovery; total daily intake matters most.
- Protein Distribution: 3–5 meals with sufficient protein and smart carbs (TEF in mind).
- Sleep & Stress: Consistent sleep (Myth #6) and cortisol regulation enhance system response.
Practice – 14-Day Orientation
- Day 0: Set your baseline: calculate BMR/TDEE, define protein intake, establish training targets and consistent sleep windows.
- Daily: Track morning weight, steps (NEAT), training intensity (RIR), and sleep duration/quality. Evaluate weekly averages.
- Pre/Post Training: Consume carb-focused meals around workouts to refill glycogen and support recovery; distribute protein to sustain MPS.
- Day 14: If Rate of Gain flattens or fatigue rises, review TDEE, surplus strategy and NEAT together.
Common Misconceptions
- “Insulin automatically makes you fat.” Fat gain requires a caloric surplus. Insulin is a signal – energy balance is the primary driver. See Myth #5.
- “High-GI carbs are always superior post workout.” Timing helps, but daily totals and context matter more. Quality and tolerance over dogma. Related: Myth #3 and SRA.
- “Insulin blocks fat loss entirely.” Temporary lipolysis inhibition is normal. Over time, calorie control and training quality determine outcomes. See Hypertrophy.
“Five to six hours of sleep are enough for muscle growth.”
Too short-sighted. Sleep drives recovery, training quality and appetite regulation – indirectly affecting insulin sensitivity and performance. Explained in Myth #6.
Studies and evidence (PubMed)
If you want to dive deeper into the research on this topic, here is a small selection of studies on PubMed:
- Skeletal muscle insulin resistance as primary defect in type 2 diabetes – Diabetes, 1987
- In vivo insulin action in muscle vs adipose tissue in humans – Journal of Clinical Investigation, 1991
Note: These papers are primarily written for professionals. They do not replace medical advice.