A photorealistic two-panel before-and-after fitness comparison of a woman showing increased muscle mass.

Create a realistic, non-sexual scientific fitness physique comparison of the same adult woman, shown from the front in a two-panel before-and-after image. She is a 35-year-old woman, 157 cm tall, with long brown hair and brown eyes, standing naturally and smiling. She wears simple, close-fitting athletic clothing consisting of a fitted sleeveless sports shirt and knee-length athletic shorts, suitable for a professional fitness assessment. LEFT PANEL — BEFORE: She weighs 48.8 kg, has a BMI of 20.6 and approximately 23% body fat. She has a naturally lean but untrained physique, with relatively little muscular development and normal healthy proportions. RIGHT PANEL — AFTER: The same woman weighs 52.8 kg after gaining exactly 4 kg of muscle while retaining the same amount of body fat. The additional muscle is realistically and proportionally distributed among the major muscle groups: shoulders, upper back, arms, core, glutes, thighs and calves. Her physique is visibly stronger and more muscular but remains natural-looking and feminine, without an exaggerated bodybuilding appearance. Keep the woman's identity, facial features, hairstyle, height, proportions, stance, camera distance, camera angle, lighting, background and clothing as consistent as possible between both panels. The only significant physical difference should be the realistic increase in muscularity resulting from 4 kg of additional muscle. Use a neutral, standardized fitness-assessment posture and straightforward Mehr sehen