The most critical factor for muscle gain is achieving the total daily protein target. The timing of intake and the number of meals are secondary details that matter far less, representing only minor optimizations once the primary goal is met.
The body's adaptation to a caloric deficit is largely behavioral. The main factor is a 200-300 calorie drop in non-exercise activity (NEAT)—less fidgeting and spontaneous movement. This behavioral change is the major component, while purely metabolic slowdowns are minor.
No single named diet is universally superior. The most effective plan for sustained weight loss has adequate protein and calories from healthy foods, but most importantly, it fits the individual's personal preferences and tolerances to ensure long-term adherence.
Studies on individuals in free-living conditions show that adding significant protein (e.g., 80-100g) on top of a normal diet can lead to a reduction in body fat. This is likely due to increased satiety, causing a spontaneous decrease in overall calorie consumption.
While animal proteins are more anabolic gram-for-gram, this difference becomes irrelevant for muscle and strength gains once total daily protein intake is sufficient (around 1.6g/kg). Controlled studies show no significant difference in outcomes between vegan and omnivore groups.
While you cannot spot-reduce subcutaneous belly fat, you can influence the loss of dangerous visceral fat around organs. Diets lower in saturated fats, specifically from fatty land animal meats, are more conducive to reducing this specific type of abdominal fat.