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Just by adding extra bananas weight gain cannot be achieved. You need to add lot more other nutrients. A balanced diet with adequate nutrients is required for weight gain. Include nutrient dense foods like nuts, non veg foods, pulses, legumes, etc. To your meal. Bananas are rich in carbohydrates, while you need more protein to build more muscle. In this way you can be more healthy.
Next Steps
For further guidance, contact directly for a detailed menu plan