HAES- Chapter One- The biology of set points

In the last posting, I introduced Chapter One of the book "Health at Every Size" by Linda Bacon. In Chapter One we learn about homeostasis and natural set points, the biological basis behind why it is so hard to lose weight and keep it off.  Dr. Bacon ends that section of Chapter One by describing a 1995 study published in the prestigious New England Journal of Medicine. The study was called Changes in energy expenditure resulting from altered body weight and was authored by Rudolph Leibel, Michael Rosenbaum and Jules Hirsch.  After Googling this citation, I found the study and read it myself.

I copied the abstract and it is at the end of this blog.

What is so interesting about this article is that it is not a fluke? Actually, there have been hundreds, HUNDREDS of studies that conclude the same thing. The bottom line- Because our bodies resist starving, a diet of fewer calories than usual will trigger the body to lower the metabolism, so as not to wander too far away from the setpoint range.  During periods of overeating when more calories than usual are obtained, the body does the opposite, revs itself up in order to burn the extra calories, again in an attempt not to wander too far from the natural set point weight. This study points out another caveat..that for overweight people, the lowering and reving up of metabolism doesn't work the same way as it does in people who had never been overweight. For overweight people who eat fewer calories, the body works even harder to lower metabolic activity and retain weight.

Don't think that the brain is not affected by this lowering of metabolic activity. In fact, the master switch for set points is the hypothalamus, located deep in the brain. Brain and body are  linked by hundreds of chemical messengers: hormones, peptides and neurotransmitters that circulate in the blood stream. Chemicals that trigger a lowering of metabolism are not limited to the hypothalamus, they also can affect emotional and motivational centers in the brain. There are at least 40 identified chemical messengers that influence these interconnected physical, mental and emotional neural circuits involved in eating and satiety.

The chapter includes a a brief discussion on two of those chemicals, leptin and ghrelin. Leptin is a chemical that signals the brain to release other chemicals that turn down the appetite, speed up metabolism and increase the desire to move. In one early study, fat mice injected with leptin lost 30% of their body weight. In another study, mice with a genetic mutation resulting in no leptin production were fat even when they are caged with normal size mice.  Another chemical, ghrelin works to increase appetite and is influenced by leptin and other gut horomones that are activated by the type and volume of food that you eat. At the same time your brain and body are getting the message to "eat" or "don't eat", there is also a response to the myriad of chemical messages associated with your emotions and generated by your sleep/wake cycle. What's more, the amount of chemical messages and the receptors that exists on target organs throughout the body is influenced by genetics. According to the "thrifty gene" theory, the humans that eventually evolved from the hunter/gatherers were NOT the ones that were likely to be thin. The humans that could resist weight lost had evolutionary advantage and we, apparently, descended from them.

The chapter ends with a set of questions related to your natural set point for weight. Some of the items are:

• Do you have difficulty recognizing when you are hungry or when you have had enough?
• Do you routinely eat beyond a comfortable level of fullness and then feel lethargic, stuffed and uncomfortabe after meals.
• Do you go through periods where you eat out of control in anticipation of soon going on a diet?
• Do you eat as a coping mechanism?
• Questions are continued.....

The author concludes that if you answer YES to any of the items  then you are likely to be above your natural setpoint. She then explains that her book will help you get to the natural set point that is the weight that is healthiest for you.

...By the end of the book, you'll be answering "yes" to these questions:

• Do you eat naturally in response to signals of hunger, fullness and appetite withou fixating on your weight or food habits?
• Is eating effortless and enjoyable?

  Soon your body will be guiding you in making nutritious, pleasureable choices.  No more counting calories, totaling fat grams or weighing broiled skinless chicken breasts!  pg 99

 I know you want to hurry up and get to the "What do I do" part of the book. But that is in Chapter 9 and my next blog will be on Chapter 2 where Dr. Bacon identifies the two major reasons for set-point change: 1) Eating for reasons OTHER THAN sensing hunger and 2) Eating foods that make us full but DON'T really nourish the body.

Want to know more? Buy the book or Stay tuned......


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N Engl J Med. 1995 Mar 9;332(10):621-8.

Abstract

BACKGROUND:

No current treatment for obesity reliably sustains weight loss, perhaps because compensatory metabolic processes resist the maintenance of the altered body weight. We examined the effects of experimental perturbations of body weight on energy expenditure to determine whether they lead to metabolic changes and whether obese subjects and those who have never been obese respond similarly.

METHODS:

We repeatedly measured 24-hour total energy expenditure, resting and nonresting energy expenditure, and the thermic effect of feeding in 18 obese subjects and 23 subjects who had never been obese. The subjects were studied at their usual body weight and after losing 10 to 20 percent of their body weight by underfeeding or gaining 10 percent by overfeeding.

RESULTS:

Maintenance of a body weight at a level 10 percent or more below the initial weight was associated with a mean (+/- SD) reduction in total energy expenditure of 6 +/- 3 kcal per kilogram of fat-free mass per day in the subjects who had never been obese (P < 0.001) and 8 +/- 5 kcal per kilogram per day in the obese subjects (P < 0.001). Resting energy expenditure and nonresting energy expenditure each decreased 3 to 4 kcal per kilogram of fat-free mass per day in both groups of subjects. Maintenance of body weight at a level 10 percent above the usual weight was associated with an increase in total energy expenditure of 9 +/- 7 kcal per kilogram of fat-free mass per day in the subjects who had never been obese (P < 0.001) and 8 +/- 4 kcal per kilogram per day in the obese subjects (P < 0.001). The thermic effect of feeding and nonresting energy expenditure increased by approximately 1 to 2 and 8 to 9 kcal per kilogram of fat-free mass per day, respectively, after weight gain. These changes in energy expenditure were not related to the degree of adiposity or the sex of the subjects.

CONCLUSIONS:

Maintenance of a reduced or elevated body weight is associated with compensatory changes in energy expenditure, which oppose the maintenance of a body weight that is different from the usual weight. These compensatory changes may account for the poor long-term efficacy of treatments for obesity.