The Science of Weight/Muscle Gain

The Science of Weight/Muscle Gain

Weight Gain Guidelines

Gaining weight, with a primary focus on building muscle, requires a daily calorie surplus in conjunction with progressive resistance training. Resistance training provides the necessary stimulus for additional calories and protein to be utilized for muscle synthesis. Without this stimulus the extra calories are converted to body fat – an undesirable result for most adults. A carefully planned nutrition and dietary support plan, including correct meal timing, and a properly designed training program can optimize muscle growth potential. In general, adult males can gain approximately half a pound of muscle per week(1) and adult females can gain over a quarter of a pound weekly.(2) However, this will vary based on age, training experience, training load, nutritional status and dietary habits.  

At present, there is lack of agreement in the scientific community as to the number of calories required to gain a pound of muscle, particularly since the energy cost of resistance training is highly variable from person to person. The energy content of muscle tissue can be calculated based on the composition of muscle which is approximately 75 percent water, 20 percent protein and the remaining materials a combination of intramuscular triglycerides, glycogen, and minerals.(3)Therefore, protein content in muscle is roughly 364 calories (~ 4 calories per gram of protein; 454 grams per pound) but the energy expended for resistance training workouts, additional activity and the metabolic activity associated with recovery and synthesizing muscle must also be factored in.  Some estimate the total energy in a pound of muscle is small compared to the energy required to stimulate muscle growth through exercise or the cost of doing exercise to maintain added muscle.  

Ideally, daily calorie intake should be slightly above needs to allow extra nutrients and calories to be deposited into muscle tissue, allowing one’s body fat percentage to naturally “drift down” as muscle weight increases. If simultaneous body fat loss is desired, then the calorie deficit should be no greater than approximately 15 percent of daily calorie requirements (maintenance) or maximum muscle building will be compromised. Otherwise, an additional 200 to 500 calories per day above daily requirements is generally recommended for optimal gains. Measurable changes to skeletal muscle fibers require regular bouts of progressively more challenging exercise for at least six to eight weeks.(4,5,6) However, calories should be increased incrementally – adding approximately 100 to 250 per day depending on body size anytime weekly weigh-ins do not reflect desired gains.

Nutritional Strategies for Weight Gain

Proper diet manipulations can dramatically and positively affect muscle-building hormone production. Accomplishing the proper hormone balance for muscle building, without increasing body fat, is a function of carbohydrates, proteins and fats being supplied in proper ratios, forms and at specific times in relation to training periods while remaining within the calorie allotment necessary for the weight gain goal. Using diet to harness the body’s most powerful muscle building hormone, insulin, can reduce muscle catabolism (breakdown) and increase muscle anabolism (buildup), offering the potential to maximize muscle synthesis. In addition to stimulating muscle protein synthesis, insulin also plays a major role in minimizing the damage caused by exercise. Strength training triggers the release of the catabolic hormones cortisol and epinephrine, which work to breakdown glycogen and muscle protein to supply energy and produce work. However, this process also leads to muscle damage. Although intense training is required to stimulate growth, tissue damage can be minimized during and after exercise, so the body spends more time utilizing incoming nutrients to build new muscle rather than constantly repairing it, thus allowing training plateaus to be avoided.

Pre- and Post-Workout Feedings

There are certain times, primarily immediately post-workout, when muscle building is at its peak. These times are referred to as metabolic windows and may last up to 90 minutes.  During the post-workout period, muscle cells become highly receptive to the incoming nutrients responsible for muscle growth. Therefore, if nutrients are low or absent, muscle building is minimal at best. Insulin is the hormone that initiates the cascade of muscle-building events during these short specific periods. By stimulating insulin at specific times with the proper carbohydrate and protein intake before, during and after exercise, cortisol and muscle breakdown can be blunted, while muscle building and energy recovery can be significantly enhanced.(7) Therefore this small “window of opportunity” requires a well-designed fast-acting formula to satisfy the muscle’s exercise-induced demands.(8)  

Numerous studies have demonstrated that the inclusion of “immediate” pre and post-training, fast-acting carbohydrate/sugar and protein feedings can stimulate muscle protein synthesis (MPS)(9.10) and reduce muscle damage to a far greater extent than normal eating patterns.(11,12) In other words, no matter how well you eat throughout the day, you recover faster and build more muscle and strength by including these quickly absorbed pre- and post-exercise formulas (see Figure 1).(13,14)

Figure 1: Training results from 23 experienced recreational bodybuilders resistance training for 10 weeks with all things (diet, supplements, training, etc.) equal except the addition of pre/post feedings yielded significantly greater gains in body mass, LBM, strength and reduction in fat mass for the pre/post feeding subjects. Adapted from Rolls et al, 2006.

Diet composition

As stated above, carbohydrates will play an important role in performance, recovery and insulin levels. Carbohydrates should make up 45 to 65 percent of total calorie intake while trying to increase muscle size. Without adequate carbohydrates, ideal insulin activation will not occur, recovery from intense workouts will not be ideal, and muscular stores of energy for the next workout may be suboptimal. None of this contributes to maximum muscular gains. Protein, which mistakenly receives the greatest focus by many exercisers, needs to be high enough to allow for tissue growth. For even the hardest training bodybuilder when calories are not severely restricted, a protein intake of up to 1 gram per pound of bodyweight is more than enough to allow for increased needs due to intense workouts and adding muscle. Higher protein intakes are not necessary and may even impede progress if it takes the place of dietary carbohydrate. The exception to this is during severe calorie restriction during the final weeks of contest preparation of physique or cosmetic athletes. (Nutritional strategies for this population are beyond the scope of this article and are published elsewhere.) Healthy fats will complete the picture, making up the remaining calories and generally supplying 15 to 35 percent of total calorie intake.

Dietary Supplements

The final component to maximizing size and performance gains is the integration of dietary supplements. The primary goal of incorporating dietary supplements into food planning is to supply specific compounds that are used during energy, force production (muscle exertion and subsequent damage) and are needed for recovery and building. This helps keep calories within an appropriate range so unwanted weight gain is avoided. Additionally, these specific compounds must be supplied in greater amounts than are used so that a portion of their intake will be deposited into the damaged or depleted structural tissues. This will lead to the desired increase in muscle size.

By isolating these nutrients and compounds from the food form, they can be ingested without calories in order to control body composition. Dietary supplements that are manufactured in proper forms and dosages allow users to deliver the needed nutrients into the body at the exact times necessary to take full advantage of periods when muscle cells are most nutrient-sensitive. This is established by training, sleep and meal times. Proper dietary supplement use including the science behind individual products is presented in a separate section of this course.


The science of weight control is rooted in energy balance and the laws of nature. Therefore, managing calories consumed and expended allows for long-term weight management. Critical components in achieving and sustaining weight control goals include becoming aware of influencing factors such as appetite and environmental forces and establishing methods to self-regulate behaviors to properly modify energy balance. Knowing daily calorie requirements, food logging, learning nutritional information, controlling portions and using meal replacements are effective weight control strategies; however, these should be recommended to clients based on lifestyle and readiness.

Optimal muscle gain requires extra calories and nutrients, ideal diet composition, pre- and post-workout feedings, proper dietary supplementation and progressive resistance training. Muscle gain will vary based on individual differences including training experience and frequency.


1  Aagaard P. Making muscles "stronger": exercise, nutrition, drugs. J Musculoskelet Neuronal Interact. 2004 Jun;4(2):165-74. Review.
2  Cullinen K, Caldwell M. Weight training increases fat-free mass and strength in untrained young women. J Am Diet Assoc. 1998 Apr;98(4):414-8.
3  McArdle WD, Kath FI and Katch VL. Exercise physiology: Energy, nutrition and human performance, Third edition. Malvern, PA. Lea & Febiger, 1991.
4  Staron RS, Karapondo DL, Kraemer WJ, et al. Skeletal muscle adaptations during early phase of heavy-resistance training in men and women. J Appl Physiol 1994;76:1247
5  Green H, Goreham C, Ouyang J, Ball-Burnett M, Ranney D. Regulation of fiber size, oxidative potential, and capillarization in human muscle by resistance exercise. Am J Physiol 1999;276:R591
6  McCall GE, Byrnes WC, Dickinson A, Pattany PM, Fleck SJ. Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training. J Appl Physiol 1996;81:2004
7  Kimball SR, Farrell PA, Jefferson LS. Invited Review: Role of insulin in translational control of protein synthesis in skeletal muscle by amino acids or exercise. J Appl Physiol. 2002 Sep;93(3):1168-80. Review.
8  Tipton KD, Rasmussen BB, Miller SL, Wolf SE, Owens-Stovall SK, Petrini BE, Wolfe RR. Timing of amino acid carbohydrate ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol Endocrinol Metab. 2001 Aug;281(2):E197-206.
9  Koopman R, Wagenmakers AJ, Manders RJ, Zorenc AH, Senden JM, Gorselink M, Keizer HA, van Loon LJ. Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects. Am J Physiol Endocrinol Metab. 2005 Apr;288(4):E645-53. Epub 2004 Nov 23.
10  Esmarck B, Andersen JL, Olsen S, Richter EA, Mizuno M, Kjaer M. Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans. J Physiol. 2001 Aug 15;535(Pt 1):301-11.
11  Bird SP, Tarpenning KM, Marino FE. Liquid carbohydrate/essential amino acid ingestion during a short-term bout of resistance exercise suppresses myofibrillar protein degradation. Metabolism. 2006 May;55(5):570-7.
12  Baty JJ, Hwang H, Ding Z, Bernard JR, Wang B, Kwon B, Ivy JL. The effect of a carbohydrate and protein supplement on resistance exercise performance, hormonal response, and muscle damage. J Strength Cond Res. 2007 May;21(2):321-9.
13  Paddon-Jones D, Sheffield-Moore M, Aarsland A, Wolfe RR, Ferrando AA. Exogenous amino acids stimulate human muscle anabolism without interfering with the response to mixed meal ingestion. Am J Physiol Endocrinol Metab. 2005 Apr;288(4):E761-7. Epub 2004 Nov 30.
14  Cribb PJ, Hayes A. Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy. Med Sci Sports Exerc. 2006 Nov;38(11):1918-25.

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