It’s because they are high in fibre, vitamins, and minerals and low in saturated fat, which helps you manage your weight, and may reduce your risk of type 2 diabetes, cardiovascular disease, and some cancers.
Some high-fibre foods also have a lower glycaemic index (GI) which means they provide a slow release of carbohydrate into the blood and help with type 2 diabetes management. The combined effect of fibre and low GI may help keep you feeling full for longer.
Indirectly, this helps you snack less and consume a less calorific meal which is what you would want to do to control your weight.
A plant-based diet tends to have less fat and saturated fat. Cutting down on saturated fat intake (by substituting with polyunsaturated fats or complex carbohydrates) reduces the risk of heart disease and stroke.