Many gym-goers and fitness enthusiasts prioritize muscle-building and a lean physique, often turning to protein shakes, bars, or powders to support their workouts. While regular exercise supports overall health, excessive reliance on protein supplements can place added strain on the kidneys, particularly among people with undiagnosed kidney conditions, and may contribute to chronic kidney disease (CKD).

Protein is an essential macronutrient needed for muscle repair, hormone production, and immune function. For most healthy adults, the Recommended Dietary Allowance is about 0.8 grams per kilogram of body weight per day. Athletes, older adults, or those with specific health needs may require slightly more. However, consuming protein beyond what the body needs does not improve performance or health and may increase kidney workload.

High protein intake can raise urea levels, increase the risk of dehydration, cause digestive discomfort, and lead to unintended weight gain. In people with reduced kidney function, excess protein may also result in the buildup of waste products that stress the kidneys. For individuals who regularly consume protein supplements, understanding personal protein requirements is crucial. Consulting a registered dietitian nutritionist (RDN) can help align intake with fitness goals while protecting kidney health.

Why appearances can be misleading

A fit appearance or a “normal” body mass index (BMI) is often assumed to reflect good health, but this is not always the case. BMI, which is based on height and weight, does not account for body composition. Highly muscular individuals may fall into overweight or obese BMI categories despite having low body fat and healthy metabolic markers. On the other hand, people with normal BMI may still carry excess visceral fat and low muscle mass, increasing their risk for metabolic disorders and CKD.

Visceral fat, the deep fat stored around internal organs, is strongly linked to diabetes, cardiovascular disease, and kidney disease. BMI cutoffs also vary by age, sex, and ethnicity. For instance, Asian populations may face higher metabolic risks at lower BMI levels, while athletes may be misclassified as obese due to muscle mass. Health experts stress that BMI should be used only as a screening tool, not a definitive measure of health.

Additional indicators such as waist circumference, waist-to-hip ratio, body fat percentage, and body roundness index can offer clearer insight into kidney and metabolic risk.