THE BIOLOGY OF HUNGER

     If you think about it, every living thing eats.  Granted that plants don’t have a mouth as we think of it but they take in minerals and water from the soil and carbon dioxide from the air and they make plant flesh out of that.  In a sense, they eat dirt and carbon dioxide in air.  All animals eat.  And the higher forms in the life chain all have a mouth which serves as a conduit to get water and nutrients into the body.  As a general rule, humans in our society eat three times a day although a few eat only once a day all day.

     Eating disorders come as the 60% of us that eat too much and the small percent of us that eat too little.  Eating too little and becoming malnourished appears to represent a psychological disease most common in young woman.  This disease is called anorexia nervosus or bulimia.  One may remember Karen Carpenter of the singing group,The Carpenters, who died of this disease at 32 years of age.  It is a very complex problem requiring intensive treatment programs.

     The more urgent problem and one that is now catapulted obesity into a leading cause of death in the United States is overeating.  In recent years, obesity has been credited with contributing to 400,000 deaths per year or about 20% of all the people that die in the United States annually.  Research efforts into the biology of hunger and how to curb hunger are becoming intense.  The cigarette problem in the United States has definitely diminished over the past 50 years although still a major problem. The overweight problem in our society is growing at a very alarming rate.

     In the past 10 years, there have substantial advances in understanding what drives a person to eat.  The simplistic and inadequate view is that overweight people simply lack discipline and give in to their whims too easily.  Two recent studies show how simplistic and inadequate this idea is.  The first experiment of nature has to do with the Phen-Fen diet pills that were prominently used from 1994 through 1997.  An extensive research program done by Dr. Weintrob showed that the Phen-fen combination lead to very substantial weight loses in very obese individuals.  An article appeared in the Readers Digest in the early 1990’s describing Dr. Weintrob’s work and that article started an epidemic.  Large numbers of overweight individuals came to the clinic requesting the Phen-Fen drug combination.  Most of these individuals only wanted the diet pills but not all of the counseling and the exercise advice and the medical aspects that might accompany a Phen-Fen program.  Instead they just wanted these pills to take and let their weight melt away.  I took care of over a thousand patients in that time who used these medications.  The most amazing number I know about a treatment trial is that there were only 4 in 1000 patients who did not lose weight using the Phen-Fen drug combination.  That is a 99.6% success rate.  I reviewed several hundred of the patients who used those medications a year later.  Contrary to the public and the FDA’s perception, I did not find even one that had a heart problem from these drugs.

     But the important point to make about this experience was that I told patients that I would prescribe the medications as they requested.  They would return in 2 weeks and if they lost weight, the prescription would be renewed.  If they did not lose weight using the prescription, then there was no reason to renew it.  The success rate was amazing and I did not ask even one of them to exercise more or to eat less.   I simply asked them to let the pills do the work and decrease the individual’s hunger if it would.  That Phen-Fen drug combination was amazingly successful.

     The lesson from that experience was that weight loss requires a decreased intake of food.  An exercise program may help some but in fact will probably stimulate an appetite more than it will burn up stored calories.  I do not deny that an intensive exercise program will help lose weight if the person exercises enough discipline to make it work.  But the Phen-Fen experience did not require exercise from anyone and they lost lots of weight.  The rule is that overweight is dependent upon how much you eat.  The second rule is that there are medications that decrease appetite and allow a person to eat less without a personal effort.  As a corollary to that experience, it might be known that the drug Fasten (Phentermine) is still on the market and felt to be a safe drug to use as an appetite suppressant.  It is only 60% as effective as the Phen-Fen combination but 60% is better than nothing.

     The second experiment of nature was the discovery of a hormone called Ghrelin.  This is the hormone made by the stomach and it drives a person to eat.  The concentration of the blood goes up between meals and drops very quickly when a person has a meal.  When a person doesn’t eat, the amount of this hormone in the blood goes up to very high levels and requires the person to exercise inordinate discipline not to eat.

     The quirk of nature  that doctors have accidentally stumbled upon, was that gastric bypass surgery turns this hormone off.  One of the major reasons that a person with gastric bypass surgery looses weight is that they are no longer hungry.  The older forms of gastric surgery to treat overweight maintained a normal route of food going through the stomach although it was impeded by the surgical procedure.  The gastric bypass surgery completely bypasses anything going through the stomach.  When this is done, the hormone Ghrelin drops to very low levels for reasons that we don’t understand but the effect is dramatic and the weight loss with gastric bypass surgery is quite dramatic. Again, people who undergo gastric bypass surgery are not asked to undertake a vigorous exercise program instead, they simply eat less.

     Hunger is much too complex and critical a phenomenon for it to be guarded by only one or two hormones.  We now know that there are hormones called leptin, ghrelin, adiponectin and protein YY, among at least 10 others that I won’t bother to name.  Each of these hormones has been clearly shown to either increase or decrease food intake in animal models.  In addition, we have found rare humans who either over produce one of theses hormones or lack one of them and indeed they are very overweight or very underweight.

     The message from this column is:
 1.  The idea that discipline alone can lead to weight control is invalid.  It works for less than 2% of our population.  Remember that a standard meal is 600 to 800 calories.  At only 100 calories per mile exercise costs too much to go burn up a meal.
 2.  Hunger is hormonally controlled.  To this time, gastric bypass surgery is the most effective method of dealing with extreme overweight.  Rather than acting as a mechanical barrier to food intake, it also functions to change the hormonal balance that a person has.
 3. The overweight problem in America has to do with how much we do eat, not how much we don’t do.  Exercise may be a help but the pivotal factor in overweight Americans is the excessive food intake they have.
 4.  There are no current diet pills as effective as the Phen-Fen program was.  But intensive research in this area is ongoing.  Some day we will find a medication that works as well as the Phen-Fen program did but doesn’t carry the stigma that was attached to fenfluramine (Pondamin, Redux).