I've lost 3 kg and I couldn't to get them back,...

Tips to gain more weight

• You need to eat more calories than your body burns to gain weight, aim for 300–500 calories per day above your maintenance level for slow weight gain or 700–1,000 calories if you want to gain weight fast.
• Protein forms the building blocks of your muscles such as chicken, beef, lamb, etc, choose fattier cuts.
• To gain weight, eat at least three meals per day and make sure to include plenty of fat, carbs and protein.
• eat nuts, almonds, walnuts, macadamia nuts, peanuts 5 times per week
• eat dried fruit, raisins, dates, prunes after lunch.
• eat high-fat dairy at breakfast such as whole milk, full-fat yogurt, cheese, cream.
• use fats and oils such as olive oil and avocado oil
• consume high amount of grains such as oats and brown rice.
• eat potatoes, sweet potatoes and yams.
• eat dark chocolate, avocados, peanut butter, coconut milk, granola, trail mixes between meals