Macros for Weight Loss
A 40% carb / 30% protein / 30% fat split is the default starting point for most people losing fat. Here's why it works, when to deviate, and how to read the scale once you start.
- Calorie deficit drives fat loss. Macros decide how much of that loss is fat versus muscle, and how miserable you feel getting there.
- 40/30/30 (carb/protein/fat) is the safe default. Higher protein (35–40%) is better for trained lifters; lower fat is fine but don't drop below 0.3 g/lb.
- Set a 15–25% deficit. Larger deficits work in the short term but cost muscle and adherence.
- Protein at 1.0–1.2 g per pound of bodyweight is the most muscle-preserving range during a deficit.
- A "plateau" usually means weeks of stalled weight, not days. Most stalls are unlogged calories, not metabolic damage.
Why a calorie deficit is the only thing that matters (and why macros still do)
Body fat is stored chemical energy. The only way to reduce it is to spend more energy than you take in over time. No food, supplement, or training style overrides this. Once you're in a deficit, however, what you eat decides:
- How much of the lost weight is muscle vs fat. Adequate protein and resistance training keep the loss almost entirely fat.
- How hungry you are. Protein and fiber dominate satiety; refined carbs and liquid calories sabotage it.
- How well you train. Carbs around training maintain workout intensity, which protects muscle.
- How your hormones behave. Fat too low (under ~0.25 g/lb sustained) tanks testosterone, sleep, and cycle regularity in women.
The 40/30/30 split, dissected
40% of calories from carbs, 30% from protein, 30% from fat. For a 2,000 kcal cut:
- Carbs: 2,000 × 0.40 = 800 kcal ÷ 4 = 200 g
- Protein: 2,000 × 0.30 = 600 kcal ÷ 4 = 150 g
- Fat: 2,000 × 0.30 = 600 kcal ÷ 9 ≈ 67 g
Why this ratio is the default:
- It puts protein high enough (around 0.9–1.1 g/lb for most adults at this calorie level) to preserve muscle.
- It keeps fat in the "happy hormones, satisfying meals" range without making the diet feel ascetic.
- It leaves enough carbs to power four to six hard training sessions a week.
If you're a lighter person on a steeper cut, the ratio shifts naturally — protein climbs as a percentage when total calories drop. That's a feature, not a bug.
How to size your deficit
The right deficit depends on how much fat you have to lose and how trained you are.
| Body fat range | Suggested deficit | Target weekly loss |
|---|---|---|
| >30% (men) / >38% (women) | 25% | 1.0–1.5% bodyweight |
| 20–30% / 28–38% | 20% | 0.7–1.0% |
| 12–20% / 22–28% | 15% | 0.5–0.7% |
| Under 12% / 22% | 10% | 0.25–0.5% |
The leaner you get, the slower you should go. Aggressive deficits at low body fat lose mostly muscle.
Three worked examples
Example 1 — Sarah, 32, 145 lb (66 kg), office job, 2 lifts/week
BMR (Mifflin-St Jeor): 10 × 66 + 6.25 × 165 − 5 × 32 − 161 = 1,371 kcal. Activity multiplier 1.4 → TDEE ≈ 1,920 kcal. 20% deficit → 1,540 kcal target.
- Protein: 1.0 g/lb × 145 = 145 g (580 kcal, 38%)
- Fat: 0.35 g/lb × 145 ≈ 50 g (450 kcal, 29%)
- Carbs: remaining 510 kcal ÷ 4 = 128 g (33%)
Roughly 38/33/29. Protein runs higher than the 30% default because Sarah is lighter and her deficit is moderate — perfectly fine.
Example 2 — Mark, 41, 220 lb (100 kg), construction worker, no formal training
BMR: 10 × 100 + 6.25 × 180 − 5 × 41 + 5 = 1,925 kcal. Activity 1.7 → TDEE ≈ 3,275 kcal. 20% deficit → 2,620 kcal.
- Protein: 0.9 g/lb × 220 = 198 g (792 kcal, 30%)
- Fat: 0.35 g/lb × 220 ≈ 77 g (693 kcal, 26%)
- Carbs: 1,135 kcal ÷ 4 = 284 g (44%)
Mark needs the carbs because his job is physically demanding. Cutting carbs too low here would crater his work capacity by week three.
Example 3 — Priya, 26, 130 lb (59 kg), trains 5×/week, last 8 lb to lose
BMR: 10 × 59 + 6.25 × 162 − 5 × 26 − 161 = 1,311 kcal. Activity 1.6 → TDEE ≈ 2,100 kcal. She's already lean, so a gentle 12% deficit → 1,850 kcal.
- Protein: 1.1 g/lb × 130 = 143 g (572 kcal, 31%)
- Fat: 0.35 g/lb × 130 ≈ 45 g (405 kcal, 22%)
- Carbs: 873 kcal ÷ 4 = 218 g (47%)
Higher carbs because Priya trains hard and her deficit is small. She should expect 0.5 lb/week and not panic at slow movement.
The thermic effect of food (a real, small lever)
Digesting food costs energy. Protein burns 20–30% of its own calories during digestion; carbs burn 5–10%; fat burns 0–3%. On a 150 g protein day (600 kcal), you spend roughly 120–180 kcal just digesting. That's not a magic bullet, but a high-protein cut effectively gives you a 100–200 kcal "free" advantage every day vs an equivalent low-protein cut. It's one more reason protein wins on a deficit.
What each macro does during a cut
Protein — the non-negotiable
During a deficit, your body breaks down both fat and muscle for energy. Adequate protein and resistance training tilt that ratio almost entirely toward fat. The research consensus for cutters is 1.0–1.2 g per pound of bodyweight (2.2–2.6 g/kg). Going higher doesn't help; going lower costs you muscle.
Fat — the hormone protector
Fat below ~0.25 g/lb sustained for weeks tends to lower testosterone in men and disrupt menstrual cycles in women. There's nothing magic about higher fat, but a floor of 0.3 g/lb (0.7 g/kg) is sensible insurance. See the fat calculator guide for more.
Carbohydrate — the training fuel
Carbs aren't required for life, but they're required for hard glycolytic training. If you lift heavy or do interval work, keeping carbs as the largest macro by gram count usually preserves performance better than an equal-calorie low-carb cut. The carb calculator guide covers timing.
Plateau troubleshooting
"I've stalled" almost always means one of five things. Work through them in order.
1. You haven't actually stalled
Three flat days is not a plateau. Two consecutive weeks with no change in 7-day average bodyweight is. Water retention from a hard training day or salty meal can hide a real loss for a week. Wait.
2. Tracking has gotten loose
Audit a week. Re-weigh oils, sauces, peanut butter, the splash of milk in coffee, the bites taken during cooking. Most stalls trace to 200–400 unlogged kcal a day.
3. NEAT has dropped
Non-Exercise Activity Thermogenesis — the calories you burn fidgeting, standing, walking around the office — falls when you cut. You unconsciously sit more, take the elevator, drive instead of walk. A step counter exposes this. Adding 2,000 daily steps is usually enough to break the stall without changing food.
4. You've genuinely adapted
After a 10–15 lb loss, your maintenance is lower than the calculator predicted. Reduce calories by another 100–150 kcal (cut from carbs or fat, never protein) and reassess in two weeks.
5. You need a diet break
If you've been in a deficit for 12+ weeks, take 7–14 days at maintenance. Hormones (leptin, thyroid) recover, hunger drops, training quality returns, and the next cutting block works better. This isn't a "cheat week" — it's structured maintenance, tracked normally.
How fast should the scale move?
A reasonable target is 0.5 to 1.0% of bodyweight per week, averaged over four weeks. For a 180 lb person that's 0.9–1.8 lb/week. Faster than that for more than two weeks at a time risks muscle loss; slower than that suggests calories aren't actually below maintenance.
When to stop the cut
Stop when you hit your target body fat, when training quality crashes for a week despite a diet break, or when life stress (sleep, work, relationships) makes adherence impossible. Then transition to maintenance macros for at least a month before any new phase. Don't bounce straight from cut to bulk.
Three full sample weeks of cutting plates
Week pattern A — Office worker, 1,700 kcal target
- Breakfast: 200 g Greek yogurt + 80 g granola + berries
- Lunch: 150 g chicken + 180 g cooked rice + big salad with 10 g olive oil
- Snack: apple + protein shake
- Dinner: 150 g salmon + roasted vegetables + 200 g potato
- Evening (optional): 100 g cottage cheese with cinnamon
Week pattern B — Lifter, 2,200 kcal target
- Breakfast: 4 eggs + 80 g oats + banana
- Lunch: 200 g chicken + 250 g rice + vegetables + olive oil
- Pre-workout: rice cakes + jam + whey scoop
- Dinner: 200 g lean beef + sweet potato + salad
- Evening: casein scoop with milk
Week pattern C — Higher protein, lower fat (35/40/25)
- Breakfast: egg whites + 1 whole egg + oats with whey-cocoa mix
- Lunch: 200 g cod + 200 g rice + salsa-heavy salad
- Snack: 200 g cottage cheese with pineapple
- Dinner: 250 g chicken + sweet potato + greens
- Evening: protein pudding (whey + cocoa + Greek yogurt)
Cardio during a cut — how much, what kind
Cardio is a tool for adding deficit when food cuts are reaching their floor. It's not magic.
- Start with daily steps (target 8,000–12,000) before adding formal cardio.
- Add 2–3 sessions/week of low-impact cardio (incline walking, cycling, rowing) of 25–40 min.
- Avoid hard interval work that interferes with lifting recovery — save HIIT for when you have margin.
- Run cardio on lifting days to keep rest days fully recovered, or separate by 6+ hours from lifting.
Body composition methods — which to trust
Scale weight is one number. Body fat estimation methods vary in accuracy:
- DEXA scan — gold standard, ±1–2% error, requires a clinic visit.
- Hydrostatic weighing / Bod Pod — also lab-grade, ±2%.
- Calipers (skinfold) — ±3–5% with experienced operator.
- Bioimpedance scales — ±5–8%, hugely affected by hydration.
- Mirror photos every 2 weeks — no number, but the most reliable everyday tool for tracking real change.
For a regular cut, you don't need lab measurement. Daily weight + tape measurements at waist/hip/thigh + bi-weekly photos cover everything.