Potential side effects of extreme dieting can include nutrient deficiencies, metabolic slowdown, and increased risk of eating disorders. Very restrictive diets may lead to physical issues such as fatigue, hair loss, or weakened immune function. Psychologically, individuals may experience heightened feelings of anxiety or depression related to their eating habits. Furthermore, extreme diets often foster an unhealthy relationship with food, making it challenging to maintain long-term weight loss goals.