Optifast has been helping people shed pounds since 1974, according to Diets in Review. The liquid diet plan is a very-low-calorie, medically supervised 12-week plan aimed at helping obese people shed their weight. As a very-low-calorie diet, or VLCD, Optifast does cause you to go into ketosis. Do not start any low-calorie weight-loss diet plan without your doctor's consent and supervision.
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If your body doesn't get enough calories or carbohydrates to use as a source of energy, it turns to fat. When fat is broken down in the liver, it creates something called ketone bodies, which it then uses as a source of energy. When you're in ketosis -- that is, you have ketones circulating in your blood -- your breath may have an acetone or fruity smell.
Optifast and Ketosis
According to the Optifast website, you are expected to go into a mild state of ketosis when following the Optifast VLCD program. You go into ketosis due to the restriction in your calorie intake. This program reduces daily calories to 800 by limiting your intake to two Optifast VLCD shakes or bars a day, plus 2 cups of nonstarchy vegetables, such as leafy greens or broccoli, and 1 teaspoon of oil. The website reports that you may lose up to 4 pounds a week during this phase of the program.
Ketosis and Weight Loss
Ketosis does help you lose weight, according to a 2014 review article published in the International Journal of Environmental Research and Public Health. The theory is that the state of ketosis helps you lose weight quickly through the breakdown of fat and through appetite suppression. The authors of the review article also noted that you may burn more calories when in ketosis.
Optifast, Ketosis and Health
While ketosis may seem like an unnatural state to be in, it does not seem to have any long-term effects on your health, according to a 2004 study published in Experimental and Clinical Cardiology. In fact, losing weight while in a state of ketosis on diets like Optifast may be beneficial to your health, according to the authors of the review article in the International Journal of Environmental Research and Public Health. While Optifast may help you lose weight, however, many people may have difficulty keeping the weight off once they start eating regular food again, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Sticking with a healthy eating plan and adding regular exercise to your weight-loss regimen will help prevent the weight gain, suggests the institute.