Bitter gourd and amla juice are generally known more for supporting digestion, immunity, and blood sugar control rather than for weight gain. Bitter gourd is low in calories and may even help with weight management in some people. Amla is rich in vitamin C and antioxidants and may improve overall health, but neither juice directly causes healthy weight gain. If your goal is to gain weight, the main focus should be on a balanced diet with enough calories, protein, healthy fats, milk products, nuts, pulses, eggs, or other nutritious foods. Regular exercise and strength training can also help increase healthy body weight and muscle mass. These juices can usually be taken either on an empty stomach or after breakfast, depending on your digestion and tolerance. However, some people may develop acidity, stomach discomfort, or low blood sugar when taking bitter gourd juice on an empty stomach, especially if they have diabetes or take diabetes medicines. In such cases, taking it after food may be better. If you are underweight without a clear reason, or if you are losing weight unexpectedly, it is important to consult a doctor for proper evaluation.