Not medical advice. I am a software engineer, not a physician. This page documents my own protocol and the research I read while building it. Talk to a qualified clinician before changing your supplementation, diet or any treatment. Lab reference ranges quoted here vary by laboratory and by individual.
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The only way to lose body fat is to consume fewer calories than your body expends. This is not a diet philosophy or opinion — it is a consequence of the first law of thermodynamics (conservation of energy). No supplement, food timing strategy, or exercise routine circumvents this fundamental principle.
When you create a caloric deficit, your body must access stored energy to make up the difference. Ideally, the majority of this stored energy comes from fat tissue (adipose tissue), though some will inevitably come from muscle glycogen and, in poorly managed deficits, from muscle protein itself.
Key equation: Energy Balance = Energy In (food/drink) - Energy Out (BMR + TEF + TEA + NEAT). A negative balance = fat loss. A positive balance = fat gain. It really is that simple at a thermodynamic level.
Total Daily Energy Expenditure (TDEE) has four components:
| Component | % of TDEE | Description |
|---|---|---|
| BMR (Basal Metabolic Rate) | 60-70% | Energy to maintain vital functions at complete rest |
| TEF (Thermic Effect of Food) | 8-15% | Energy to digest, absorb, and process food |
| TEA (Thermic Effect of Activity) | 5-10% | Planned exercise and training |
| NEAT (Non-Exercise Activity Thermogenesis) | 10-20% | Fidgeting, walking, standing, daily movement |
To estimate BMR, the Mifflin-St Jeor equation is the most validated formula (Mifflin et al., 1990, studied 498 subjects):
Men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5
Women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161
Then multiply by activity factor: Sedentary (1.2), Lightly active (1.375), Moderately active (1.55), Very active (1.725), Extremely active (1.9)
Important: NEAT is highly variable and often underestimated. Levine et al. (1999) at the Mayo Clinic found that NEAT varied by up to 2,000 calories/day between individuals. This is why two people with similar body composition and exercise habits can have very different caloric needs.
Levine, J. A., et al. (1999). Role of nonexercise activity thermogenesis in resistance to fat gain in humans. Science, 283(5399), 212-214. PubMed
A deficit of 500 calories per day produces approximately 0.5 kg (1 lb) of fat loss per week. This is based on the approximation that 1 kg of body fat contains approximately 7,700 calories (3,500 per lb). This rate is considered optimal for most people because it:
For individuals with more fat to lose (BF% >25% for men, >35% for women), a larger deficit of 750-1000 calories/day can be tolerated with less muscle loss risk. For leaner individuals (BF% <15% men, <25% women), a smaller deficit of 250-500 calories is advisable.
There is a physiological limit to how much fat your body can mobilize and oxidize per day. Alpert (2005) calculated this limit at approximately 69 calories per kilogram of body fat per day (31.4 kcal/lb). This means:
Example: A 80 kg man at 20% body fat has 16 kg of fat. His maximum daily fat oxidation is 16 x 69 = 1,104 calories/day from fat. Any deficit beyond this will increasingly come from muscle tissue. As he gets leaner (say 12% = 9.6 kg of fat), his maximum drops to 662 cal/day, requiring a progressively smaller deficit.
Alpert, S. S. (2005). A limit on the energy transfer rate from the human fat store in hypophagia. J Theor Biol, 233(1), 1-14. PubMed
This concept has profound practical implications: the leaner you get, the slower you must diet. Attempting an aggressive deficit when already lean is the fastest path to muscle loss.
Very low-calorie diets (VLCDs, typically <800 calories/day) produce rapid initial weight loss but fail long-term for several interconnected reasons:
Fothergill, E., et al. (2016). Persistent metabolic adaptation 6 years after "The Biggest Loser" competition. Obesity, 24(8), 1612-1619. PubMed
Metabolic adaptation (also called adaptive thermogenesis) is your body's survival response to prolonged caloric restriction. It reduces energy expenditure beyond what would be predicted by the loss of body mass alone. This adaptation occurs through several mechanisms:
Trexler et al. (2014) reviewed the evidence and estimated that metabolic adaptation typically amounts to a 5-15% reduction in expected energy expenditure during prolonged dieting. This means a person who "should" be burning 2,000 calories may only be burning 1,700-1,900.
Trexler, E. T., et al. (2014). Metabolic adaptation to weight loss: implications for the athlete. JISSN, 11, 7. PubMed
Two evidence-based strategies can mitigate metabolic adaptation:
Refeeds are planned periods (typically 1-2 days) where caloric intake is raised to maintenance level, primarily through increased carbohydrate intake. The purpose is to temporarily boost leptin, replenish muscle glycogen, and provide a psychological break. Research suggests refeeds are most effective when carbohydrate-focused, as carbohydrates have the strongest effect on leptin signaling.
The MATADOR study (Byrne et al., 2018) is the strongest evidence for diet breaks. 51 obese men were randomized to either 16 weeks of continuous caloric restriction or alternating 2 weeks of deficit with 2 weeks of maintenance (totaling 30 weeks but the same 16 weeks of deficit). The intermittent group lost 47% more fat, had significantly less metabolic adaptation, and retained more weight loss at 6-month follow-up.
Byrne, N. M., et al. (2018). Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. Int J Obes, 42(2), 129-138. PubMed
Body recomposition — simultaneously losing fat and gaining muscle — was once considered impossible. However, research has shown it is achievable in specific populations:
Barakat et al. (2020) conducted a systematic review of 18 studies on body recomposition and confirmed that it occurs most reliably in untrained, overweight individuals who combine resistance training with a moderate caloric deficit (10-25% below TDEE) and high protein intake (2.0-2.4 g/kg/day).
Barakat, C., et al. (2020). Body Recomposition: Can Trained Individuals Build Muscle and Lose Fat at the Same Time? Strength Cond J, 42(5), 7-21. PubMed
GLP-1 receptor agonists (semaglutide, tirzepatide) have transformed pharmacological weight loss since 2023. The SEMALEAN study (2025) tracked body composition changes during semaglutide treatment and found that while lean mass initially declined by ~3 kg at month 7, it stabilized thereafter, and handgrip strength actually improved by +4.5 kg at month 12. The prevalence of sarcopenic obesity decreased from 49% to 33%. However, lean mass losses of 26-40% of total weight loss remain a concern with GLP-1 monotherapy. The BELIEVE trial demonstrated that combining bimagrumab with semaglutide achieved 22.1% weight loss with 92% from fat mass, the best body composition outcome seen to date.
For those using GLP-1 medications, current best practice (2025-2026) recommends resistance training 3-5 days per week and protein intake of 1.2-1.5 g/kg of ideal body weight daily (80-120 g for most adults) to mitigate lean mass loss. Adding structured exercise to semaglutide therapy cuts lean mass loss roughly in half compared to medication alone.
SEMALEAN Study (2025). Impact of Semaglutide on fat mass, lean mass and muscle function in patients with obesity. PMC. PubMed Central