Stop Starving Your Colony: The Real Truth About RimWorld Biotech Metabolism
Metabolic Efficiency Calculator
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What is Metabolic Efficiency?
In RimWorld's Biotech expansion, metabolic efficiency is a gene-derived stat that directly affects how much food your pawns need to eat. Every gene has a metabolic efficiency impact (positive or negative) which sums up to the pawn's total efficiency stat.
Positive Efficiency
High values (+1 to +5) mean the pawn needs less food. A pawn with +5 efficiency only needs half as much food (50% hunger rate).
Negative Efficiency
Low values (-1 to -5) mean the pawn needs more food. A pawn with -5 efficiency needs 225% food (more than double normal intake).
Important: Metabolic efficiency -5 is the lowest possible in vanilla RimWorld. The gene assembler won't let you create a xenogerm with lower than -5 efficiency.
Gene interface displaying metabolic efficiency values and their impact on hunger rates
Efficiency Reference Table
| Efficiency | Hunger Rate | Nutrition/Day | Game Impact |
|---|---|---|---|
| +5 | 50% | 0.8 | One meal per day |
| +3 | 70% | 1.12 | 30% less food needed |
| +1 | 90% | 1.44 | Slightly less hungry |
| 0 | 100% | 1.6 | Baseline human (2 meals/day) |
| -1 | 125% | 2.0 | Need 25% more food |
| -3 | 175% | 2.8 | Need 75% more food |
| -5 | 225% | 3.6 | Need 125% more food (4+ meals/day) |
Default Xenotype Efficiency
RimWorld's base xenotypes each have a default metabolic efficiency level:
| Xenotype | Efficiency | Hunger Rate | Notes |
|---|---|---|---|
| Neanderthal | +2 | 80% | 20% less food needed |
| Hussar | +2 | 80% | Engineered soldier, efficient |
| Genie | +1 | 90% | Slightly less food |
| Dirtmole | +1 | 90% | Slightly less food |
| Baseliner (Human) | 0 | 100% | Normal human metabolism |
| Highmate | 0 | 100% | Average appetite |
| Impid | 0 | 100% | Genes balanced out |
| Sanguophage | 0 | 100% | Has Archite Metabolism (+6) |
| Pigskin | -1 | 125% | 25% more food needed |
| Yttakin | -1 | 125% | 25% more food needed |
Note: No default xenotype has metabolic efficiency -5. Xenotypes with -5 are almost always custom-created or result from gene inheritance.
Xenotype selection interface displaying various metabolic efficiency ratings for different races
Gene Effects on Metabolic Efficiency
Beneficial Genes (Lower Efficiency)
These genes give advantages but increase hunger (negative efficiency):
- -2 Strong Melee Damage (+50% melee damage)
- -2 Strong Shooting (improved accuracy)
- -2 Fast Runner (increased movement speed)
- -2 Fire Spew (Impid fire-breathing ability)
- -1/-2 Tough Skin (damage resistance)
- -1 Kind Instinct (always kind, no abrasive)
- 0 Archite genes (Perfect Immunity, No Pain, etc.)
Detrimental Genes (Raise Efficiency)
These genes give disadvantages but decrease hunger (positive efficiency):
- +6 Archite Metabolism (special gene in Sanguophages)
- +4 Kill-Thirst (needs to kill or gets mood debuff)
- +3 Violence Disabled (cannot fight at all)
- +2 Never Sleep (no sleep need but -15% consciousness)
- +2 Slow Runner (reduced movement speed)
- +1 Poor/Awful skill genes (e.g., Poor Cooking)
- +1 Ugly (reduced social impact)
Designing Balanced Xenotypes
When creating xenotypes, you need to balance beneficial and detrimental genes to achieve your desired metabolic efficiency. The gene assembler won't let you finalize a xenogerm below -5 efficiency.
For combat-focused pawns, consider adding "irrelevant" negative traits (like Poor Artistic or Poor Cooking) to offset combat genes if your soldier doesn't need those skills.
Gene assembler showing how beneficial and detrimental genes balance metabolic efficiency
Strategies for Managing -5 Metabolic Efficiency
1. Boost Food Production
If someone eats 2.25× normal, you need to produce 2.25× food to keep pace:
- Increase crop farming: Dedicate an extra field just for this pawn. If you farm 10 rice plants per normal colonist, farm ~22 for a -5 pawn.
- Focus on hunting and ranching: Supplement with extra meat from hunting or slaughtering animals.
- Trade for food: Keep silver reserves to buy food from traders when they visit.
- Build emergency food reserves: Always have pemmican or survival meals tucked away.
- Use a Nutrient Paste Dispenser: It converts 0.3 nutrition of raw food into a 0.9 nutrition meal – tripling efficiency of your ingredients.
Tip: Plan your colony's food around your hungriest pawn. If you have one -5 pawn and 4 normal pawns, treat it like you have 6-7 pawns total when calculating food needs.
Colony food production layout optimized for supporting high-metabolism colonists