1️⃣ The Paradox of the “Puffy but Under-eating” Athlete
You’re training hard.
You’re meticulous with food.
And yet… you still feel puffy, bloated, and flat.
It’s frustrating — especially when you’re doing everything “right.”
But here’s the reality:
If you’ve been chronically under-eating while pushing high training volume, your body’s stress systems are working against you — not because you’re broken, but because your physiology is protecting you.
2️⃣ The Stress Response: When Low Energy Becomes a Survival Threat
Your body doesn’t distinguish between “I’m in a famine” and “I’m under-fueling for a CrossFit cycle.” Both signal energetic stress.
That stress activates your HPA axis (hypothalamic–pituitary–adrenal axis) — your built-in survival system:
- The hypothalamus releases CRH (corticotropin-releasing hormone).
- The pituitary releases ACTH (adrenocorticotropic hormone).
- The adrenal glands pump out cortisol.
Cortisol’s job: keep blood glucose available so your brain and essential organs don’t run out of energy.
3️⃣ Cortisol 101: How It Rewires Energy Use
Cortisol mobilizes energy by:
- Stimulating gluconeogenesis (the liver making glucose from protein).
- Increasing protein breakdown (especially in muscle tissue).
- Antagonizing insulin in muscle and fat cells.
That last part matters.
When cortisol “blocks” insulin’s action in your muscles and adipose tissue, those cells can’t efficiently take up glucose.
So blood sugar stays higher — preserving fuel for the brain and vital organs.
Short-term, that’s adaptive.
Long-term (in a chronically under-fed, over-trained state), it becomes a problem.
4️⃣ How High Cortisol Leads to Water Retention
Cortisol isn’t just about stress or glucose — it also affects fluid regulation through multiple mechanisms:
➤ Sodium Retention
Cortisol can bind to mineralocorticoid receptors, increasing sodium reabsorption in the kidneys.
Where sodium goes, water follows — so you literally start holding onto fluid.
➤ RAAS and Vasopressin Activation
Your stress response upregulates the renin–angiotensin–aldosterone system (RAAS) and vasopressin (ADH).
Both hormones conserve fluid and prevent diuresis (water loss).
In plain terms: your body won’t “let go” of water easily.
➤ Inflammation and Microtrauma
Under-recovery and high training loads cause low-grade inflammation. Cytokines like IL-6 and TNF-α make capillaries leakier — letting plasma seep into tissues.
You see that as swelling, puffiness, or bloating.
➤ Low Glycogen + Osmotic Shifts
Each gram of glycogen binds roughly 3 grams of water.
Chronically depleted glycogen stores, plus altered sodium/potassium balance, shift water from inside your cells (where it supports muscle tone) to outside the cells (where it looks like “bloat”).
5️⃣ The Fix: Restore Energy Availability
You can’t out-supplement or out-train this.
You fix it by feeding the system consistently.
🔬 What “Maintenance” Actually Means
Maintenance calories =
The amount of energy your body needs to:
- Maintain your weight,
- Recover from training,
- Support normal hormonal function, and
- Keep non-exercise movement (NEAT) steady.
It’s not a single number — it’s a range that allows your physiology to feel safe again.
If you’ve been under-eating for months or years, your true maintenance might be several hundred calories higher than what you think.
6️⃣ The Maintenance Phase: 4–6 Months of Metabolic Recovery
Think of this phase as a recovery protocol, not a bulk.
During a true maintenance phase (4–6 months minimum), you give your body what it needs to:
- Normalize cortisol output and HPA sensitivity.
- Restore glycogen and intracellular fluid balance.
- Rebuild lean tissue and mitochondria.
- Re-sensitize insulin and growth-promoting pathways (IGF-1, thyroid, sex hormones).
- Re-establish normal RAAS and vasopressin signaling so your body stops clinging to water.
This is where the “flat and puffy” look starts to fade — and your lean mass, shape, and performance return.
7️⃣ Action Steps to Reverse Stress-Induced Water Retention
1. Eat at true maintenance for 4–6 months.
Increase calories gradually (~200–300 kcal per week) until your body weight stabilizes and your performance, sleep, and recovery improve.
2. Prioritize macronutrient balance.
- Protein: 1.6–2.2 g/kg of bodyweight
- Carbs: 4–6 g/kg (key for cortisol reduction and glycogen restoration)
- Fats: 0.8–1.0 g/kg (supports hormones and recovery)
3. Hold training volume steady — not maximal.
Fuel recovery rather than chasing more output.
4. Protect circadian rhythm.
Consistent sleep (7–9 h/night) anchors cortisol regulation.
5. Shift into parasympathetic recovery modes.
Breathwork, walking, low-intensity cardio, time in nature — anything that calms the sympathetic drive.
6. Keep sodium and hydration balanced.
Low sodium + high cortisol = worse retention.
Aim for adequate sodium (2.5–3.5 g/day) and potassium from whole foods.
8️⃣ What Happens When You Get It Right
After a few weeks of consistent fueling:
- Water retention starts to decrease.
- Energy levels and training quality rebound.
- Recovery and sleep dramatically improve.
- Mood, libido, and mental clarity come back online.
- Your “hard work” finally starts to show.
You don’t need to “cut harder” — you need to feed smarter.
💥 Ready to Fix It for Good?
You don’t need to cut harder — you need to feed smarter.
The Fueled Athlete Jumpstart is your 7-day reset designed to restore energy balance, lower cortisol, and get your body responding to training again.
It’s not another diet — it’s the exact system I use with my athletes to help them rebuild metabolism, normalize stress hormones, and finally see the lean, toned look they’ve been working for.
👉 Join the Fueled Athlete Jumpstart and learn how to fuel like an athlete — not a dieter.
🔬 References
- McEwen BS. Physiology and Neurobiology of Stress and Adaptation: Central Role of the Brain. Physiol Rev. 2007;87(3):873–904.
- Harrell CS et al. Energetic Stress: The Reciprocal Relationship Between Energy Availability and the Stress Response. Front Physiol. 2015.
- Areta JL et al. Physical Performance During Energy Deficiency in Humans. Curr Opin Clin Nutr Metab Care. 2023.
- Angelidi AM et al. Relative Energy Deficiency in Sport (RED-S): Recent Updates. Endocr Rev. 2024.
- Stachowicz M et al. The Effect of Diet Components on the Level of Cortisol. Eur Food Res Technol. 2017;243(4):519–527.
- De Kloet ER, Joëls M, Holsboer F. Stress and the Brain: From Adaptation to Disease. Nat Rev Neurosci. 2005;6(6):463–475.
- The Renin–Angiotensin–Aldosterone System in Stress and Cardiovascular Physiology. J Clin Endocrinol Metab. 2020;105(3):e762–e775.
- Waterhouse M et al. Vasopressin and Cortisol Interactions in Stress Physiology. Int J Mol Sci. 2024;25(13):7394.