While carb-free, high-protein diets do offer results, Willow, of C&J Nutrition added, it's not sustainable or healthy for the long term, as you're missing out on vital nutrients from fruits, veggies, beans, nuts, seeds, and whole grains. This variety of healthy foods "helps keep your gut bacteria happy, your digestive system regular, and keeps you feeling satisfied." So you don't want to be downing protein smoothies all day.
Registered dietitian and personal trainer Jim White, ACSM, told POPSUGAR that the standard dietary reference for protein intake is approximately 0.8 to 1.2 grams of protein per kilograms of bodyweight. So on the contrary, not getting enough protein can also cause weight gain, since protein helps you to stay satisfied. If you're worried about getting enough, aim to eat it at every meal and snack.