The Science of Weight Loss

Dr. Blackburn serves as Associate Professor of Surgery and Nutrition, Associate Director of the Division of Nutrition, and is the first incumbent of the S. Daniel Abraham chair in Nutrition Medicine at Harvard Medical School. He is the, Chief of the Nutritional/Metabolism Laboratory, and Director of the Center for the Study of Nutrition Medicine, which are affiliated with the Beth Israel Deaconess Medical Center in Boston, Massachusetts.

  • Transcript


George Blackburn:  I really developed a field at the Harvard Medical School that brought the science of nutrition together with the science of medicine.  I did that through a PhD in nutritional biochemistry from MIT, after already having trained as a physician and trained as a surgeon.  Now when the field started the problem was that in surgery there were people who could not eat and would not eat due to their surgery, and they were starving to death.  So I was sent to MIT to the unit of experimental medicine to try to dissect out this problem and see what alternatives we could create, and found an alternative to sugar water, to amino acids and vitamins and minerals so that we could stop the starvation and allow people the time they needed to recover from their surgery and recover from their wounds before starving to death.  From that I needed people to simulate the starvation of surgery.  And so much to my surprise people came out of the woodwork wanting to volunteer to lose weight.  I knew nothing about obesity.  I was amazed by their interest.  But they were flabbergasted by the capacity to lose weight under this structured semi-starvation.  Now that was, you know, good for surgery, it turned out that's a good way to lose weight but it wasn't a good way to keep weight off.  So what we learned from that was, and was the breakthrough that I was able to make is that really what was possible was to lose ten percent of your body weight.  That was a great medical benefit for diabetes, for hypertension, for cardiovascular disease.  But if you try to lose more weight than that it was like stretching an elastic band, that it would snap back.  So people who lost more weight than that or lost it too fast would regain the weight.  That was demoralizing, and of course didn't achieve the goal of a long-term weight loss to a healthier goal.

Question: What inspires your work?

Blackburn:  I think from my experience these things are all serendipitous.  The classical post-graduate work for a surgeon is to go to the National Cancer Institute and undertake the study of cancer for which surgery is a major part of the treatment.  But there was this discovery at the University of Pennsylvania of another way to feed patients, but there wasn't any science.  There was no nutritional science behind it.  It was clearly mechanical at that approach.  So that going to MIT and finding this unit of experimental medicine within a department of nutrition science was accidental, but I took advantage of that.  It gave me an answer to the problem that I was sent to MIT to do.  It provided great benefit, led to merging, as I pointed out, the science of nutrition with the science of medicine.  Professional societies were formed first for the starving surgical patients giving them what's called parenteral and enteral nutrition, this is intravenous and oral feeding.  But on the other hand, we lay the groundwork that physicians could get involved with the treatment of obesity, which they were not.  That was not thought to be a legitimate activity of any physician, certainly not a surgeon.

Question: What do we know about weight loss?

Blackburn:  Well, we know enough.  We know that our body weight each day is controlled by the genes we inherited from our parents and the environment, and the exposure to food.  And that combination of hunger from our genetic development and the availability of food will lead to some caloric intake that will be compared to the energy we spend to do our activity.  Over the last 20 years, from 1980 to 2000, that's been an imbalance, so that the population, in fact, gained 24 pounds.  Now to gain 24 pounds, since you need a minimum of 10 calories to sustain every pound of your body weight, and then activity you in fact need another five calories for a total of 15 calories, that means that the population was suddenly eating somewhere between 250 and 400 more calories.  You can see the devastation of that because we already were at a healthy weight in 1980, and adding this 25 pounds just caused an epidemic of weight-gain related problems, which were diabetes, which were hypertension, which were cardiovascular disease, and in my area of interest in certain cancers.  And there's just a myriad of other diseases that are caused by weight gain.

Question: Why are Americans fat?

Blackburn:  Well, there's a lot of speculation.  Certainly our genes didn't change, so we can't blame it on our parents or our genetic background.  So then that exposes us to the environment, and it could either be the 24/7 availability of food, the availability of the caloric density of food, or the fact that now we were so busy that the activity that we were burning before 1980 was reduced, and the same calories we were eating were not offset by the same energy expenditure, and therefore we gained weight by being too sedentary.

Question: What can we do to stop expanding?

Blackburn:  Well, we certainly want education.  We know that we're asking the restaurants to allow the people who buy food to know how many calories there are here in New York City.  We think that that's a good idea.  We think that food labels should be able to inform the individual the size, the detail, nutrition information that's on our food which are the healthy foods and which are, you know, the foods without any nutritional benefit.  So that would be called a mark.  So we do believe in education.  We don't see where the regulation of rules is going to be as powerful as the desire of everybody to want to eat healthy.  And if they know how many calories they're eating, that'll give them the opportunity to make a decision, including to eat less.

Question: What is Food First?

Blackburn:  It's very important to realize that, you know, the best choice that a person can make now is that you are what you eat.  Yes, the activity is a factor, but overwhelmingly the evidence is that as we change the diet just to reduce 200 or 300 calories, that you will start to lose weight and get to this ten percent weight loss.  Now the exercise is good for keeping the weight off, but exercise is not a good way to burn fewer calories to lose weight.  So Food First means that in your common sense or in your decision-making, every time you have an experience with food you ought to make it healthy, it ought to be proportion-controlled, and it ought to fit into a healthy diet when you put your breakfast, lunch and dinner together each day.

Question: How can we learn to eat less?

Blackburn:  This is one the things that we think people don't understand.  When you pick up or choose food and you put it in your mouth, you get satiation.  You get the taste of it.  But it takes 20 minutes for that food to enter your stomach, enter into your intestine and activate hormones to tell your brain that you ate.  So that this fast rush eating that we're doing and not allowing those 20 minutes to take place robs us of the opportunity to get a signal from the food we've eaten that we've eaten enough, that the hunger is gone and that we have the satiation, and that's enough food.  When you think about it it's a simple practice.  But, you know, like everything, anything you want to excel in, any sport, any profession, you know, it takes time.  So you really need a clock to know the minute you start eating, take a little bit of the food that you're consuming from each portion, from the vegetables, from the starch, from the meat, fish or fowl in this area, and allow ten minutes to take place while there's still just a quarter of the food eaten.  Then you take another five minutes for another quarter, and another five minutes for another quarter.  Now three-fourths of food are eaten and the bell has rung, twenty minutes have taken place.  Your brain now knows what you ate, you know, particularly in calories.  And it now can feed back to you that you're no longer hungry and that you're starting to feel full.  And now you look down and you see there's a quarter of the food left, you can leave that behind.  That's the opposite of the clean plate.  But that's so valuable, because just leaving that little food around-- behind, will allow you to eat less, to eat healthy, to not be hungry.  And with the weight loss that comes from that, you're luck, going to feel good.