Most people building muscle need about 20 to 35% of their daily calories from fat, which typically works out to 0.5 to 1.0 grams per kilogram of body weight. That range keeps your hormones healthy, supports recovery, and leaves enough room in your diet for the protein and carbohydrates that directly fuel muscle growth. Going below 15% of calories from fat for extended periods risks hormonal disruption and nutrient deficiencies that can quietly undermine your progress.
The Recommended Range
The World Health Organization sets a floor of 15 to 20% of total calories from fat for most adults, based on what’s needed to absorb essential nutrients and maintain basic hormonal function. For people actively training to build muscle, sports nutrition guidelines generally recommend 20 to 35% of calories from fat during a gaining phase. During a cut or contest prep, physique athletes sometimes drop to 10 to 25% of calories, but that’s a temporary strategy designed to free up room for more carbohydrates, not a long-term approach.
In grams, competitive bodybuilders typically consume around 0.7 to 0.8 grams of fat per kilogram of body weight. For an 80 kg (176 lb) person, that’s roughly 56 to 64 grams of fat per day. Female competitors have been documented going as low as 0.35 g/kg during the final weeks before a show, but that extreme restriction carries real tradeoffs. If you’re in a standard muscle-building phase and eating in a caloric surplus, aiming for 0.7 to 1.0 g/kg gives you plenty of flexibility while keeping your hormones and energy in a good place.
Why Fat Matters for Muscle Growth
Fat doesn’t build muscle the way protein does. It doesn’t fuel heavy sets the way carbohydrates do. But it plays a critical supporting role that’s easy to underestimate. Your body uses dietary fat to produce hormones, absorb key vitamins, protect cell membranes, and manage inflammation from training. Cut fat too low and those systems start to falter, which can slow your gains even if your protein and training are dialed in.
One of the most important connections is between fat intake and testosterone. A systematic review of intervention studies found that men on low-fat diets had significantly lower levels of total testosterone, free testosterone, and dihydrotestosterone compared to men on higher-fat diets. The effect was even more pronounced in men of European ancestry. Testosterone is one of the primary hormonal drivers of muscle protein synthesis, so chronically low fat intake can chip away at your body’s ability to respond to training.
There’s also a dose-response relationship between dietary cholesterol (found in fat-containing animal foods) and lean mass gains during resistance training. A study of older adults doing 12 weeks of high-intensity resistance exercise found that those who ate more cholesterol gained more lean mass, independent of protein intake. Cholesterol is a building block for steroid hormones and cell membranes, both of which matter during periods of muscle remodeling.
Fat-Soluble Vitamins and Recovery
Vitamins A, D, E, and K all require dietary fat to be absorbed in the small intestine. Each one plays a role in how well you recover from training and how effectively your muscles function.
- Vitamin D regulates muscle cell function and muscle strength. People who are deficient commonly experience muscle weakness, fatigue, and a greater risk of falls.
- Vitamin E acts as an antioxidant that protects cell membranes from oxidative damage, the kind of damage that accumulates during intense exercise.
- Vitamin K contributes to muscle function, and deficiency has been linked to muscle weakness.
- Vitamin A supports nerve signaling and proprioception. Severe deficiency can reduce muscle strength and impair reflexes.
If your fat intake drops too low, you absorb less of these vitamins even if you’re eating plenty of vegetables and taking supplements. This doesn’t mean you need to eat large amounts of fat, but it does mean that very low-fat diets (under 15% of calories) put you at risk for subtle deficiencies that accumulate over weeks and months.
Does the Type of Fat Matter?
Less than you might think, at least for muscle growth specifically. A controlled trial comparing overfeeding with polyunsaturated fat (from sources like vegetable oils and nuts) versus saturated fat (from sources like butter and coconut oil) found no difference in lean tissue accumulation over eight weeks. The same pattern held in a large population-based analysis: swapping one type of fat for another didn’t change lean mass outcomes in a meaningful way.
That said, the type of fat you eat still matters for overall health. Unsaturated fats from fish, olive oil, nuts, and avocados support cardiovascular health and may help manage the chronic low-grade inflammation that comes with hard training. You don’t need to obsess over your fat sources for muscle-building purposes, but a mix of whole-food fats is a reasonable approach for someone who plans to train for years, not just months.
How to Set Your Fat Intake
Start by setting your protein target (typically 1.6 to 2.2 g/kg for muscle building). Then allocate about 25 to 30% of your remaining calories to fat. Fill the rest with carbohydrates. For most people in a muscle-building phase, this naturally lands around 0.7 to 1.0 g/kg of fat per day.
Here’s what that looks like in practical terms for a few different body weights:
- 70 kg (154 lb): roughly 50 to 70 grams of fat per day
- 80 kg (176 lb): roughly 55 to 80 grams of fat per day
- 90 kg (198 lb): roughly 65 to 90 grams of fat per day
If you’re in a caloric deficit trying to lose fat while preserving muscle, you can drop toward the lower end of that range (around 0.5 to 0.7 g/kg), but avoid staying below 15% of total calories for more than a few weeks. The International Society of Sports Nutrition notes that a wide range of dietary approaches, from low-fat to low-carb, can be effective for improving body composition. The key variable isn’t hitting some magic fat number. It’s making sure you don’t go so low that your hormones, vitamin absorption, and energy levels start working against you.
One useful signal: if your energy feels flat, your libido drops, or your skin and hair become noticeably dry during a muscle-building phase, your fat intake may be too low. Bumping it up by 10 to 15 grams per day and holding for two to three weeks is a simple way to test whether fat was the bottleneck.