Is An Energy Surplus Required To Build Muscle?
The review shows beginners and overweight lifters can pack on size in a deficit, while the optimal energy intake for experienced athletes remains scientifically unproven.
For decades, we’ve insisted that packing on muscle requires eating in a calorie surplus, consuming more energy than you burn. But this review by researchers from the University of the Sunshine Coast, the Australian Institute of Sport, and several international institutions shows that the relationship between energy intake and muscle growth is far more complex than that.
This review tackles the question: Do you actually need to eat more calories to maximise muscle growth from resistance training? While textbooks commonly recommend energy surpluses ranging from 360 to 955 calories per day, we also know that muscle growth can occur during energy deficits, too. Particularly in training newcomers and those carrying excess body fat, no rigorous controlled studies have actually determined the optimal calorie surplus for experienced lifters.
Aim
This review aimed to examine whether an energy surplus is required to maximise skeletal muscle growth in response to resistance training. If so, to explore critical practical questions, including how large that surplus should be, which macronutrients should provide the extra energy, and when throughout the day that additional energy should be consumed.
The authors wanted to address gaps in the scientific literature, noting that while protein intake recommendations for muscle growth have been extensively researched, the specific energy requirements remain poorly understood. The review also aimed to identify the energetically expensive processes involved in muscle tissue generation beyond simply the energy stored in the tissue itself, including the metabolic cost of protein synthesis, resistance training, and adaptive responses to overfeeding.
Methods
As a narrative review rather than an experimental study, the authors synthesised existing research from multiple areas, including resistance training studies, overfeeding investigations in sedentary populations, energy balance research, protein metabolism studies, and nutrient timing trials.
The review examined studies investigating energy deficits and muscle growth, overfeeding studies in twins and controlled metabolic wards, preliminary resistance training studies that provided energy supplements, and research on macronutrient distribution and timing. The authors included both acute metabolic studies measuring muscle protein synthesis over hours and chronic training studies lasting weeks to months.
Given the scarcity of direct evidence on energy surpluses combined with resistance training, the authors also analysed overfeeding studies in non-training populations to understand the metabolic responses to excess energy intake. They acknowledge that resistance training significantly alters sensitivity to nutritional interventions.
Results
Muscle Growth Without a Surplus
The review found compelling evidence that muscle growth can occur in energy deficits, particularly among certain populations. In one study, 21 women consuming a very low-energy diet (3,369 kilojoules per day, approximately 805 calories) for 90 days while resistance training showed no additional loss of fat-free mass compared to the control group, but muscle biopsies revealed increased cross-sectional area of fast-twitch muscle fibers.
Another investigation of 31 women engaging in 24 weeks of combined resistance and endurance training found that thigh muscle cross-sectional area increased by 7 square centimetres despite a 2.2% loss in body weight. Similarly, resistance training newcomers who were overweight and consumed a substantial energy deficit (approximately 60% of estimated needs) while maintaining high-protein intake (2.4 grams per kilogram daily) gained lean body mass.
Energy Surplus and Body Composition
When examining overfeeding without resistance training, the review found that sedentary people consistently gained more fat than lean mass. In a landmark twin study, 12 pairs of identical male twins were overfed by 4,200 kilojoules daily (roughly 1,000 calories) for 100 days, resulting in an average gain of 5.4 kilograms of fat mass but only 2.7 kilograms of fat-free mass—a ratio of approximately 2:1 favouring fat gain.
However, protein intake during overfeeding mattered significantly. An 8-week metabolic ward study found that while all groups consuming a 40% energy surplus gained similar amounts of fat (approximately 3.5 kilograms), only those consuming 15% or 25% of total energy from protein gained lean mass (approximately 3 kilograms). Those consuming just 5% protein from total energy gained no lean mass despite the calorie surplus.
Resistance Training Plus Energy Surplus
The limited research combining energy surpluses with resistance training showed promising but not definitive results. In one 8-week study, only those who consumed an energy-dense liquid supplement twice daily on training days showed significant gains in body weight and fat-free mass, regardless of whether the supplement was carbohydrate alone or carbohydrate plus protein. This suggested that when protein intake is already adequate, the total energy content matters more than the specific macronutrient source.
The True Energy Cost of Muscle Growth
The review revealed that traditional calculations dramatically underestimate the energy cost of building muscle. While 1 kilogram of skeletal muscle tissue contains approximately 5,000-5,200 kilojoules of stored energy (200 grams protein, 50 grams fat, and some glycogen), the actual cost of tissue deposition is substantially higher, estimated at 6,050 to 7,440 kilojoules per kilogram based on obesity research.
This additional cost accounts for the energy required for protein synthesis itself (approximately 3.6 kilojoules per gram of protein synthesised), the energy cost of resistance exercise (300-600 kilojoules per typical 30-minute session for females and males respectively), elevated muscle protein synthesis for 24-48 hours post-exercise, increased resting metabolism from new muscle tissue (though only about 54 kilojoules per kilogram per day), and adaptive responses including diet-induced thermogenesis and non-exercise activity thermogenesis.
Protein Requirements
A meta-regression of 49 studies including 1,863 participants found that protein intake of 1.6 grams per kilogram body weight per day was associated with the greatest muscle mass gains. Exceeding this amount provided no additional benefit and simply increased amino acid oxidation. Even extremely high protein intakes, up to double the recommended amount, failed to further enhance muscle or strength gains.
Carbohydrate and Fat Considerations
The review found no significant difference in body composition changes whether the energy surplus came predominantly from carbohydrate or fat in sedentary populations. However, chronically restrictive carbohydrate intake (ketogenic diets) consistently impaired muscle mass gains in resistance-trained people compared to moderate carbohydrate intakes. The recommendation remained 4-7 grams of carbohydrate per kilogram daily for strength athletes, with higher amounts for those combining resistance training with sport-specific training.
For dietary fat, intakes below 15-20% of total energy should be avoided as they reduce meal plan energy density and may modestly reduce testosterone levels. The type of fat may matter, with polyunsaturated fats more likely to promote lean mass gains compared to saturated fats, and omega-3 fatty acids showing potential for enhancing the anabolic response to nutrition.
Nutrient Timing
The review found mixed evidence for nutrient timing strategies. While some research showed benefits from consuming a carbohydrate-protein-creatine supplement immediately before and after training compared to away from training, other studies using protein-only supplements found no timing effect. The impact of distributing protein intake across 4 versus 6 meals per day showed no difference in lean body mass gains among rugby athletes.
Emerging evidence suggested that eating more total daily energy later in the day may be associated with obesity and metabolic dysfunction, though this remains to be investigated in resistance-training populations attempting to gain muscle mass. The review also noted that athletes typically don't adjust energy intake to match training days versus rest days, despite elevated muscle protein synthesis persisting for up to 48 hours post-exercise.
Practical Takeaways
Start Conservative With the Surplus
The most important practical recommendation is to take a conservative approach to creating an energy surplus, starting within the range of approximately 360-480 calories per day. This modest surplus minimises fat gain while still providing substrate for muscle growth. The review emphasises regular monitoring of body composition and functional capacities, like strength, to personalise dietary intake further.
Training Status and Body Composition Matter
Resistance training newcomers and those carrying excess body fat have a much greater capacity to build muscle in an energy deficit or at maintenance compared to lean, experienced lifters. If you’re new to serious training or have body fat to lose, aggressive calorie surpluses are unnecessary and counterproductive. The energy cost of muscle growth can be met from stored body fat in these populations.
Hit Your Protein Target
Aim for 1.6-2.2 grams of protein per kilogram of body weight daily, with 1.6 grams appearing to be the threshold for maximising muscle growth. Going beyond this range offers no additional muscle-building benefits and may simply displace other nutrients. There’s no evidence that very high protein intakes (above 2.5 grams per kilogram) are harmful for healthy people over one year, but longer-term safety data are lacking.
Don’t Fear Carbohydrates
Maintain carbohydrate intake within 4-7 grams per kilogram body weight daily, particularly if you’re training with high volume or combining resistance training with sport-specific work. Chronically low carbohydrate intake consistently impairs muscle gains in resistance-trained people. The source of your energy surplus doesn’t appear to matter for body composition outcomes as long as minimum macronutrient needs are met.
Strategic Eating Patterns
Consider consuming 5-6 eating occasions per day (three main meals plus strategic snacks) to make it easier to achieve an energy surplus without excessive fullness. Liquid nutrition sources may be particularly helpful as drinks are less satiating than solid foods while still providing quality nutrients. Consume moderate rather than gigantic servings of protein at each meal (approximately 0.3 grams per kilogram) to optimise muscle protein synthesis while managing satiety.
Individualise Based on Response
The review makes clear that individual responses to energy surpluses vary substantially due to genetics, age, training history, and metabolic adaptations. Some people dramatically increase non-exercise activity and heat production when overfed, essentially “burning off” much of the surplus, while others are more efficient at storing excess energy. This means universal recommendations are impossible. Track your body composition and strength changes over 2-4 week periods and adjust accordingly.
Mind the Gaps
The review reveals that science hasn’t definitively answered whether experienced, lean lifters truly need a calorie surplus to maximise muscle growth, or whether surplus energy should be provided only on training days versus throughout the week. Until better research emerges, a modest daily surplus with close monitoring remains the most prudent approach for those prioritising muscle gain over maintaining very low body fat levels.
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Reference
Slater, G. J., Dieter, B. P., Marsh, D. J., Helms, E. R., Shaw, G., & Iraki, J. (2019). Is an Energy Surplus Required to Maximise Skeletal Muscle Hypertrophy Associated With Resistance Training. Frontiers in Nutrition, 6, 464717. https://doi.org/10.3389/fnut.2019.00131
You can also find me at dannyleejames.com for stories, personal training insights, and coaching.
This is a really solid breakdown, Danny. I like how clearly you separate what we actually know from what people assume, especially around beginners versus experienced lifters. The takeaway that a small, monitored surplus beats aggressive bulking feels both sane and overdue.