Norwitz had been an elite long-distance runner since his teenage years and was highly successful in his first year of competition. However, he soon began experiencing
recurrent, unusual fractures, which not only reduced his training mileage but also required prolonged recovery periods. After years of repeated fractures, including a crack in one of the block-like bones in the midfoot during sprint triathlon training, he was diagnosed with
osteoporosis
, with bone density comparable to that of a 70–80-year-old. Physicians initially suspected
Relative Energy Deficiency in Sport (RED-S)
a condition in which chronic under-fueling impairs bone health and hormonal balance. Therefore, assumed he was not “eating enough,” suggesting that insufficient energy intake had impaired bone maintenance. The nutritional advice he received was to increase his intake of sugar and carbohydrates. Around this same period, he developed severe
ulcerative colitis
, a chronic inflammatory bowel disease. The condition progressively worsened, leading to dramatic weight loss, repeated hospitalizations, and profound effects on his mental and social well-being. He has publicly described periods in which the disease became
life-threatening
. This occurred while he was pursuing doctoral research in metabolism at the University of Oxford. He began to question whether conventional medical treatments would lead to durable remission. After years of attempting various dietary strategies including low-FODMAP, vegan, and elimination-style approaches without lasting success, he eventually turned to a
ketogenic diet
, a very low-carbohydrate, high-fat dietary pattern designed to shift metabolism toward fat oxidation and ketone production. According to his own accounts,
within a short period his energy improved and inflammatory markers declined. He has stated that subsequent clinical evaluation showed
resolution of active intestinal inflammation
. Following his recovery, Norwitz expanded his academic focus to lipid metabolism, inflammation biology, and LDL cholesterol physiology. He later conducted research affiliated with Harvard Medical School, where he contributed to discussions around cholesterol metabolism in low-carbohydrate diets. Today, Norwitz is active in public communication, aiming to
bring metabolic health discussions into mainstream conversations
. His work centers on cholesterol physiology, particularly in the context of carbohydrate restriction, and on re-examining how LDL cholesterol is interpreted within modern risk models.