How much protein do we really need while in a caloric surplus?

The general public has always been confused as to which diets are the ideal fit to sustain health and longevity to live a long and disease-free life. Examples include diets that are high in protein, low in carbs, high in fat, low in fat, or high in carbs.

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Athletes are an example of people who require extensive information surrounding fitness and nutrition and muscle building is usually required when starting out. Furthermore, there are underweight individuals who struggle to gain weight. In both cases a need is gain weight in a healthy way is called for. What defines healthy weight gain? Most athletes would mention that they would like to gain muscle rather than fat because increasing lean body mass will increase your metabolism since muscles are a metabolically expensive entity. Which macronutrient partitioning should be used for maximal muscle growth and minimal fat gain?

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A study published in the Journal of the American Medical Association took a single-blind randomized controlled trial which included 25 male and female volunteers with a body mass index between 19-30 and aged 18-35. The participants first consumed a diet (15% of energy from protein, 25% from fat, and 60% carbohydrates) for 13-25 days designed to yield information about their basal caloric needs. The following 8 weeks patients were fed 40% calories higher than their basal caloric requirements. There were three groups in this study 1) Fed a low protein diet (6% of energy from protein, 52% from fat, and 42% from carbohydrates) 2) Fed a moderate protein diet (15% of energy from protein, 44% from fat, and 41% from carbohydrates) 3) Fed a high protein diet (26% of energy from protein, 33% from fat, and 41% from carbohydrates).

The low protein group had significantly lower changes in weight and lean body mass than the other groups. The high protein group and the moderate protein group didn’t have statistically significant differences in weight change, accumulation of fat, and changes in lean body mass.

Figure 1. Body Composition Changes from 8 weeks of Overfeeding

The data shows that changes in body composition can be highly affected by protein intake since the amount of protein you should be consuming according to the American dietary Acceptable Macronutrient Distribution Range (ADMR) is 10%-30% calories coming from protein for adults. The low protein group was only taking in 5% of their calories from protein and the results show that this resulted in a loss of lean body mass which is uncharacteristic when you’re in a caloric surplus. This means that the group that had 5% energy from protein was likely in a state of negative nitrogen balance which means that muscle breakdown exceeded muscle synthesis and due to lack of essential amino acids being present to replace the muscle that is broken down from regular muscle movement, the result is a loss in lean body mass which is undesirable while gaining weight.