Protein sparing modified fasts (PSMF) are the most rapid
yet safe weight control diets. Known by names like Optifast
these usually take the form of five liquid "meals"
by mixing a dry powder with water. These liquid
diets usually provide about 500 calories daily along with
some minerals and electrolytes. They contain a carefully calibrated amount of carbohydrate (in order to reduce protein loss through gluconeogenesis) but still, these diets are strongly ketogenic.
Because ketosis suppresses hunger, many patients find these diets surprisingly painless. Because ketosis causes large shifts in
fluids and electrolytes in the body, patients need close medical monitoring during their time on the fasts. They also usually require additional prescription electrolyte replacement.
typically produce very rapid weight loss. Some studies show that obese
patients placed on PSMF's lost about thirty pounds of body fat in six
weeks. One particularly famous patient was Oprah Winfrey whose first major public weight loss occured in the late 1980's using a PSMF
. Unfortunately, Ms. Winfrey's success after stopping the fast was
rather typical for some patients: rapid weight regain accompanied by
irrepressible hunger. Indeed, largely because of Winfrey's public re-grain, PSMF's fell into widespread public disfavor by the early
Today, PSMF's have a limited but important role in medical
weight control. These diets are generally reserved for patients who have
an urgent need for weight loss, often an upcoming surgical proceedure (including bariatric surgery) or very serious weight related medical
problems. Used appropriately, these diets can produce results that
no other diet can match.