Nuts, seeds, nutrition and storage.
Nuts are high in calories because they pack a lot of fat into very little water: a 1-ounce serving usually provides about 155–200 calories. That does not make them nutritionally poor; most of their fat is unsaturated, and the same handful also provides protein, fiber, vitamins and minerals.
Nuts are calorie-dense, but that does not mean they automatically cause weight gain. Controlled trials have not found a meaningful increase in body weight when nuts are added to eating patterns; the practical question is how much you eat and what the nuts replace.
Almonds and pistachios lead the tree-nut ranking, but the number that matters in your hand is smaller: a 1-ounce serving gives roughly 6 grams of protein, not the 20-plus grams suggested by a 100-gram table.
Hemp and pumpkin seeds can nearly match chicken breast for protein when everything is compared per 100 grams. The difference shows up on the plate: seed servings are usually around an ounce and provide roughly 5–9 grams.