Difficulty gaining weight can occur due to low calorie intake, poor appetite, stress, irregular meals, digestive problems, excessive physical activity, thyroid issues, or other underlying medical conditions. Healthy weight gain usually occurs gradually by improving nutrition, muscle strength, sleep, and overall lifestyle, rather than relying on quick weight-gain products alone. Eating frequent balanced meals with enough protein and healthy calories may help improve body weight over time. Foods such as milk, eggs, curd, nuts, peanut butter, bananas, rice, potatoes, pulses, chicken, fish, and healthy homemade snacks may support healthy weight gain. Strength exercises, light gym training, and proper sleep are also important because they help build muscle and improve body strength naturally. Avoid relying on steroid-based medicines or unverified supplements because they may cause unhealthy fat gain and side effects. Drinking enough water and reducing stress may also support better appetite and digestion. A medical evaluation may be useful if you have sudden weight loss, poor appetite, diarrhoea, weakness, thyroid symptoms, or difficulty gaining weight despite eating properly and following a healthy routine.