The influence nutrition has on the body – the science behind bodybuilders

«Sculpted like a greed god» – a phrase used to describe an athletic, toned aesthetic of the human body with defined muscles and hardly any body fat. This kind of body shape has been fascinating people since ancient times. It was reflected in painting studios and sculptures. Polykleitos was a Greek sculptor, who, almost 2,500 years ago, wrote a canon in which he described the perfect proportions of the human body. Michelangelo later made a significant contribution to the introduction of human anatomy into art between 1475 and 1564 AD. It was only much later, in modern medicine, that we began to look at body composition.

What are we made of?

What is the human body made of? The question sounds trivial, but the answer’s not simple. That’s because your body composition changes over your lifetime. Be it through the growing process, ageing process, illness or pregnancy. Your body composition also depends on your physical activity and nutrition. Both can have a significant influence on it. This becomes visible in the extremes of malnutrition or undernourishment as well as obesity. As body composition has a major influence on health, it’s become a field of research in several areas of science. In my field, sports physiology, this is a key area of interest. We use it to measure and evaluate training interventions, returning to sport after injury or when studying the ageing process in athletes.

There are different ways of looking at body composition. Researchers use the five-level model, which considers the atomic, molecular, cellular, tissue-organ level and the level of the body as a whole.

Anatomically, for the most part, we consist of six elements. Oxygen accounts for the largest proportion (61%), followed by 23% carbon, 10% hydrogen, 2.6% nitrogen, 1.4% calcium and 0.83% phosphorus, with sulphur, potassium, chlorine and magnesium also making up less than 1% [1].

On a molecular level, we consist of about 60% water, 20% fats, 14% proteins, 5% minerals and 1% glycogen [1].

On a cellular level, body composition includes cell mass and extracellular space. The body cell mass is the sum of all cells and the extracellular space, which contains the extracellular fluid and solids. These include bone minerals, proteins and glycogen and make up around 7–8% of body mass [2].

On the tissue and organ level, we consist of fatty tissue (on average about 20% of body mass in men and 30% in women), muscles (42% and 38% respectively in women) and bones (about 7%). A further 8% is accounted for by blood. The remaining parts include the skin, liver, central nervous system, intestinal tract and lungs [1]. Several methods are used to measure body composition, such as dual X-ray absorptiometry or computer or magnetic resonance imaging.

Muscle mass makes up the largest proportion of body mass. This amounts to about 21% of the body mass after birth and increases during the course of life. While it accounts for around 42% of an adult’s body mass, it’s only around 27% in old age [3]. Muscles consist of about 75% water and 20% protein. The remaining 5% are carbohydrates, inorganic salts, minerals and fats [4]. The elements in the muscle that can generate force consist of proteins. An increase in muscle mass therefore goes hand in hand with an increase in the protein content in the muscle.

The fifth level, the body as a whole, won’t be covered in this article.

How do these elements work?

Skeletal muscle mass is regulated by a continuous process that builds up and breaks down muscle mass [5]. This process is also known as myofibrillar protein synthesis (MPS). Myofibrillar protein breakdown is referred to as MPB for short. Muscle mass is relatively constant from adulthood up until the fifth decade of life. This is from the protein we consume in our diet, which promotes protein synthesis [6-8]. Phillips and his team showed that strength training consisting of either a concentric or eccentric leg extension exercise, performed for eight sets over eight repetitions and at 80% of 1-RM, increased MPS and MPB in eight untrained participants (four men and four women) [9]. Compared to MPB, which returned to baseline 48 hours after training, MPS was still significantly higher than baseline (P < 0.01). If the MPS is greater than the MPB, the net balance is positive and the protein content increases. That’s when muscle grows. Strength training therefore means that the MPS lasts longer and sensitises the muscle to the dietary protein. If we now add an adequate amount of protein, we can promote muscle growth. As you can see, proteins are an essential component of a healthy diet, as they provide amino acid precursors for protein synthesis and other metabolic processes in the body.

Fats, carbohydrates and protein

Fats, carbohydrates and proteins are also called macronutrients. These are chemical compounds that differ in their composition and energy density. Fats have the highest physical energy density. One gramme of fat provides about nine kilocalories (kcal). Compared to carbohydrates with four kcal or protein with four kcal per gramme, this is more than twice as much. Macronutrients are therefore energy sources that can be used in the muscle to generate mechanical processes from chemical energy. However, the metabolic processes in our bodies are different. While fats have a high energy density, this energy is only obtained slowly. Carbohydrates provide less energy, but release it quicker.

Nutrition plays an essential role for our well-being and our health. It’s also an indicator of our life expectancy. That’s why it plays an important role in exercise. On the one hand, it serves as an energy source and supports recovery. On the other hand, it supports hypertrophy.

What do strength athletes eat?

Slater and Phillips published a guideline on this topic in 2011 [10], which also covers bodybuilding. The data was compiled on the basis of dietary habits taken from other publications. Bodybuilders consumed around 41 ± 10 kcal per kg of body mass. For someone weighing 85 kg, this corresponds to approximately 3,521 ± 827 kcal per day. The macronutrient intake was made up as follows: 4–7.7 g carbohydrates per kg body mass, 1.7–2.8 g protein per kg body mass. Bodybuilders cover 5–39% of their daily requirement with fats. This of course depends on the corresponding training or competition preparation phases. They consumed around 30 ± 4 kcal per kg of body mass. Their diet consists of 3.5–5 g of carbohydrates and 1.5–2.0 g of protein per kg of body mass. 7–28.1% of their daily energy requirement was covered by fats, depending on the phase they were in.

In 2018 [11], Chappel, Simper and Barker analysed the nutritional strategies of 51 competitive bodybuilders. They did this during the competition preparation period of 22 ± 9 weeks. Among other things, they compared the top five men and women against the other participants. During the preparation period, the participants reduced their daily energy intake. What they noticed was the top five men had a higher carbohydrate intake (5.1 vs 3.7 g/kg body mass) at the beginning of the preparation phase compared to the participants outside the top five. The authors speculated that this contributed positively to the maintenance of muscle mass during the preparation phase.

The composition of macronutrients for the five top-placed men and women at three points in time, measured in grammes per day during competition preparation was as follows:

The starting weight in the competition preparation phase was 82.5 ± 10.4 kg for the top five men and 64 ± 9.5 kg for the women. During the preparation for the competition, the body mass of the men decreased by 9.4 ± 5.6 kg and that of the women by 10.2 ± 5.4 kg.

Nutrition in weight training: training, recovery and aesthetics

Nutrition isn’t just essential for exercise. It significantly contributes to a longer, healthy life [12]. But it’s particularly vital for sport because it influences your training, recovery and how you adapt. Strength training is the culmination of the interplay between nutrition, training, recovery, adaptation and aesthetics. The latter, you might say, is in the eye of the beholder. Body composition is the key part of this sport. The six-pack visible in (strength) athletes is directly related to body composition. If the body fat percentage is correspondingly low, the underlying muscles are better emphasised. And through diet they can regulate their body composition.

References

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7. Bohé J, Aili Low JF, Wolfe RR, Rennie MJ. Latency and duration of stimulation of human muscle protein synthesis during continuous infusion of amino acids. J Physiol. John Wiley & Sons, Ltd; 2001;532: 575–579. doi:10.1111/j.1469-7793.2001.0575f.x
8. Fujita S, Dreyer HC, Drummond MJ, Glynn EL, Cadenas JG, Yoshizawa F, et al. Nutrient signalling in the regulation of human muscle protein synthesis. J Physiol. John Wiley & Sons, Ltd; 2007;582: 813–823. doi:10.1113/JPHYSIOL.2007.134593
9. Phillips SM, Tipton KD, Aarsland A, Wolf SE, Wolfe RR. Mixed muscle protein synthesis and breakdown after resistance exercise in humans. https://doi.org/101152/ajpendo19972731E99. American Physiological Society Bethesda, MD ; 1997;273. doi:10.1152/AJPENDO.1997.273.1.E99
10. Slater G, Phillips SM. Nutrition guidelines for strength sports: Sprinting, weightlifting, throwing events, and bodybuilding. J Sports Sci. 2011;29: S67–S77. doi:10.1080/02640414.2011.574722
11. Chappell AJ, Simper T, Barker ME. Nutritional strategies of high level natural bodybuilders during competition preparation. J Int Soc Sport Nutr. Journal of the International Society of Sports Nutrition; 2018;15: 1–12. doi:10.1186/s12970-018-0209-z
12. Longo VD, Anderson RM. Nutrition, longevity and disease: From molecular mechanisms to interventions. Cell. The Authors; 2022;185: 1455–1470. doi:10.1016/j.cell.2022.04.002