Fat Loss
Guides, research reviews, comparisons, product recommendations and FAQs for fat loss.
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Fat Loss Guide
Evidence-based beginner and intermediate guide.
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The Science of Fat Loss
Fat loss ultimately requires sustained energy deficit — but the type of exercise, the protein intake, and the rate of loss all determine whether you lose fat or muscle. The evidence consistently shows that what you do alongside the caloric deficit matters as much as the deficit itself.
Donnelly et al. (2009) — ACSM position stand. ≥250 min/week of moderate-intensity activity produces clinically significant weight loss. 150–250 min/week prevents weight gain. <150 min/week is insufficient for weight loss without dietary restriction.
PubMed 19127177 →Willis et al. (2012) — RCT comparing aerobic, resistance, and combined training. Aerobic training was most efficient for fat mass reduction; resistance training preserved lean mass; combined training produced the best body composition outcomes but required significantly more time.
PubMed 23019316 →Trapp et al. (2008) — 15 weeks of HIIT vs steady-state in young women. HIIT group lost significantly more subcutaneous fat including trunk fat, despite shorter exercise duration. Time-efficient advantage of HIIT is real but not always superior for absolute fat loss when total work is equated.
PubMed 18197184 →Stiegler & Cunliffe (2006) — review on fat-free mass retention during weight loss. Resistance training + high protein (>1.8 g/kg/day) is the most effective strategy to preserve lean mass during caloric restriction. Cardio-only dieting without resistance training loses ~25–30% of weight from muscle.
PubMed 16526835 →Fat Loss FAQs
How large should my caloric deficit be?
A deficit of 300–500 kcal/day is supported as the "sweet spot" for fat loss while preserving lean mass in most individuals. Larger deficits (>750 kcal/day) accelerate scale weight loss but disproportionately increase muscle loss and hormonal disruption (reduced testosterone, thyroid, leptin). Slower loss rates (0.5–1% bodyweight/week) produce better body composition outcomes than rapid weight loss approaches.
Is cardio or weights better for fat loss?
Willis et al. (2012) showed aerobic training burns more calories per session and produces more fat mass reduction than resistance training alone. However, resistance training preserves lean mass, which maintains resting metabolic rate during a deficit. The evidence-based answer: combine both. Aerobic training for caloric expenditure; resistance training to prevent the lean mass loss that makes weight regain likely.
Is fasted cardio more effective for fat loss?
The evidence does not support fasted cardio as superior for fat loss over matched-intensity fed-state cardio when total daily caloric intake is controlled. Short-term studies show higher fat oxidation during fasted sessions, but 24-hour fat balance studies find no meaningful difference. If fasted cardio improves your adherence or performance, it is a valid strategy — but the mechanism is not "fat burning", it is total caloric deficit.
How much protein do I need when cutting?
Stiegler & Cunliffe (2006) and subsequent research recommend ≥1.8–2.4 g/kg/day during caloric restriction to protect lean mass — higher than the protein target for maintenance or muscle building phases. The anabolic resistance caused by energy deficit means you need more protein, not less, to achieve the same muscle-preserving effect.
Why does fat loss stall after a few weeks?
Metabolic adaptation — the body reduces total energy expenditure in response to caloric restriction through reduced NEAT (non-exercise activity thermogenesis), lower resting metabolic rate, and hormonal changes (leptin, ghrelin, thyroid). Diet breaks of 1–2 weeks at maintenance calories every 6–8 weeks have research support for partially resetting these adaptive responses and improving long-term fat loss outcomes.
Do fat burner supplements work?
The only ingredients with reproducible, meaningful evidence in humans are caffeine (3–6 mg/kg improves exercise performance and increases caloric expenditure by ~5–11%) and possibly green tea extract (modest thermogenic effect, ~80 kcal/day in some studies). All other "fat burning" compounds have insufficient or industry-funded evidence. No supplement overrides a sustained caloric surplus.