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During the this past 12 years of my weight-loss maintenance, I’ve been collecting data about my food and weight. This provides me with a great deal of personal information, and that data tells me that … over the years … my weight is continuing to creep upward, even though I keep reducing my calorie intake.

I find this fact very annoying, as well as perplexing.

Until I was faced with this personal information, I believed what our Culture teaches:  “If Fat people cut back on their food intake enough to reach a “normal” weight, their bodies will become like the bodies of “normal” people. To maintain that weight loss, they need to eat more than they did to lose the weight, but not go back to eating as they did previously: in a gluttonous manner.”

Essentially, I thought that you diet down to your goal weight number; cross the finish line; and from that time on you will maintain your weight-loss by eating like normally thin people do.

This is NOT what has been happening for ME. So, I began wondering why? What’s going on?

I spent a lot of time studying books, and articles, and research about this issue, and learned that as a “reduced obese” person, what has been happening to ME, personally, seems to fall within the theories of Set Point, and Biological Adaptation. 

My History

I’ve spent my lifetime dieting, from my youth into my old age. I’ve lost, and regained, hundreds of pounds of fat.  About 25 years ago, at age 48, I had an open RNY gastric bypass surgery, which - at the time - was still considered experimental.  This forced me to eat in a way that dropped my BMI from a 52.9 BMI = Stage 4 - Super-obese, down to a  31.4 BMI = Stage 1 - just over the border of obese.  After a few years I began actively dieting again in order to avoid a rapid regain.

About 13 years ago, around age 60, I was back up to a 38 BMI = Stage 2 -Severe obesity. I began logging my food and daily weight into a computer software diet program.  I begun losing weight, and about 16 months later, in January 2006, I reached my goal of a 22.5 BMI = in the middle of the "Normal" weight range.

During the 12 years since that time, now almost age 73, I’ve continued using a computer program to log my food and daily weight.  As a result of that effort, I’ve maintained my weight at-or-near a BMI range of “normal”. I now also have 13 years of records showing my personal daily food and weight data.

The Secret Life of Fat, the Science Behind the Body’s Least Understood Organ and What it Means for You,  by Sylvia Tara, PhD (2017)

This book brings cutting-edge research together with historical perspectives to reveal fat's true identity: an endocrine organ that is critical to our health.

The Secret Life of Fat is not a diet book.  It’s a book about how fat works, about understanding body fat - specifically, its role, why it is so difficult to fight, and how it works differently for different people.

Beginning with the question “Why is it easier for some people to stay thin than others?”  Biochemist, Sylvia Tara, investigates the biology of fat and its vital purposes in the body, from reproduction to immunity. Then she examines the genetic, dietary, and other types of influences on body fat. 

She states:

“Fat enhances our brain size, strengthens our bones and immune system, helps wound healing, and can even prolong our lives.”

“Through its most powerful messenger, leptin, fat can influence our appetites. 

It can cause our muscles to reduce their energy usage. 

It can alter our sympathetic nervous system, and control the flow of hormones such as thyroid, adrenaline, and noradrenaline. 

Most profoundly, it can influence our thoughts and elicit stronger responses to food, lower our inhibition to eating, and cause us to misjudge how much we’ve eaten. 

Fat, it turns out, is capable of mind control !”

“Once we swallow food we each process it differently.  Science has shown us that food affects our hormones, and hormones affect our fat.  Insulin, leptin, ghrelin, adiponectin, estrogen, testosterone, thyroid, and other hormones influence our weight.”

Biology explains why it’s so hard to keep off the weight once you’ve lost it: People who are at a particular weight because of dieting, metabolize food differently than people who are at that same weight naturally. “Somehow, the remaining body fat of the reduced-obese,” Tara writes, manages “to survive on fewer calories than before, as though it had found another means to thrive.”

After discussing the scientific nature of fat, Tara describes her own weight struggles, and recommends persistence as the main tool for dieters, combined with any diet that is “customized for you biologically, psychologically, and socially”.

Once fat cells reach a certain size -- that is, they become filled to capacity with fat content -- then new fat cells will begin to form.  The fat cell number and size increases and shrinks based on deposits from food intake.
“We have a seemingly infinite capacity to recruit new fat cells, but we cannot get rid of them once they have been recruited" said Michael Rosenbaum, associate professor of clinical pediatrics and medicine at Columbia University. "in most cases, weight gain initially reflects ... enlargement of existing fat cells followed by an increased growth of new fat cells.”

Research has shown that obese people who have weight loss surgery have just as many fat cells two years after the surgery as before it, even though they have become much thinner.

Scientist, Dr. Rudy Leibel, says that "the body controls the number of its fat cells as carefully as it controls the amount of its fat". Fat cells die and new ones are born throughout life. Scientists have found that fat cells live for only about seven years and that every time a fat cell dies, another is formed to take its place.

Below see a 2017 New York Times article about this matter.

Are Fat Cells Forever?
              By Alice Callahan  
       February 17, 2017 - New York Times

Once fat cells are formed, can you ever get rid of them?

The number of fat cells in a person’s body seems to be able to change in only one direction: up. Fat cell number increases through childhood and adolescence and generally stabilizes in adulthood.

But this doesn’t mean that fat cells, or adipocytes, are stagnant. The size of individual fat cells is remarkably variable, expanding and contracting with weight gain or weight loss. And as with most cell types in the body, adipocytes die eventually.

“when old ones die, they are replaced by new fat cells,” said Dr. Michael Jensen, an endocrinologist and obesity researcher at the Mayo Clinic. Cell death and production appear to be tightly coupled, so although about 10 percent of adipocytes die each year, they’re replaced at the same rate.

Even among bariatric surgery patients, who can lose massive amounts of weight, the number of fat cells tends to remain the same, although the cells shrink in size, studies show.

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