The Optavia diet is quite restrictive, with most people averaging about 800-1000 calories daily. Since it is so restrictive, weight gain will likely occur after transitioning out of the diet. According to the National Library of Medicine, weight loss due to calorie restriction causes an “energy gap.” This energy gap means those on restrictive diets will be hungrier and have less energy, which signals their body to crave and eat more calories, leading to weight gain.
Restricting calories dramatically can also lead to a slowed metabolism, which can also cause weight gain. According to Healthline, eating too low of calories (under 1000 per day) can trick your body into believing food is scarce. So, your body will lower the rate of calories it burns to account for the scarcity.