Understanding the Hormonal Explanation of Obesity–#3 in our Lasting Weight Loss Series

Image of a molecule,


For a really long time, we’ve been teaching (and have been taught) that weight gain and weight loss are all based on the simple idea of how many calories we take in and how many calories we burn.   If we eat 2000 calories in a day and burn 2000 calories that same day with our activities, we should not be gaining weight.

If it’s so simple, then why are so many physicians—who have committed their lives to keep others in good health—overweight?  And more so, why are so many intelligent, ambitious and accomplished people struggling for years with being overweight or obese?

Unfortunately, this model doesn’t include a lot of variables, what determines calories out?   What about the storing of fat?  We all know people who eat way more than we think they’re burning, and they are not gaining weight.   We have many of us cut significant calories for some period of time without being able to maintain that new, starvation earned weight.  It is not all just personal failing, there’s something wrong with this model.  You can go here or here to read more about why it’s not just this simple.

So, what’s going on?

It’s very important to understand the hormonal obesity theory.  The idea that there are hormonal signals in the body that regulate fat storage in the body, like how thyroid hormone regulates the thyroid gland.    Currently, the primary hormone we understand to cause increased fat storage is insulin.  Cortisol (stress hormone) also has a role to a lesser degree.   There are likely other hormones that partake in the regulation of fat storage, but insulin is the main player.  There are studies and studies that show weight gain correlates with insulin doses in diabetics.  We know the opposite to also be true.  If you know anything about type 1 diabetes (when the body makes too little insulin), not only does a person’s sugars reach very high levels, but they can’t store any fat and start wasting away (until they get treated with insulin).  So, for most people, think of insulin as the gatekeeper of fat storage.

This also explains why it does matter if you get your calories from cake or salmon.   Cake, mostly refined carbs, causes a spike in your insulin levels.   Salmon, which has no carbs, has minimal effect on insulin.   Since insulin is the main determinate of whether or not fat is stored, the different type of calorie determines whether or not fat can be stored, not the number of calories.

There are also other issues at play that exacerbate fat storage:

  • Increased intake of carbs–the subsequent higher levels of insulin over time—causes the body to be insulin resistance
  • Insulin resistance requires the body to produce higher levels of insulin to manage the same of amount of carb intake to keep your blood sugars normal. These higher levels of insulin make the body store even more fat
  • More fat stores, in turn, increase your insulin resistance too
  • We know that Cortisol (stress hormone) also increases insulin, which adds to weight gain
    • This is why long term stress causes weight gain
    • This is why sleep deprivation causes weight gain


What about leptin?

Leptin is a hormone that is produced by fat cells.  The way it’s supposed to work, a person eats, as food is stored as fat, the fat cells release leptin, making the person feel full and stop eating.  This has kept people for centuries and millennia from becoming obese.

What’s changed is refined carbs.  As the amount of carbs in the diet has increased through refined carbs and processed foods, people have developed increased insulin levels.  Increased insulin levels block the leptin signal to the brain, allowing people to keep eating


Take home:

  • Weight gain and weight loss are not as simple as calories in and calories out
    • Eating less doesn’t cause weight loss: it increases hunger and the body will decrease its metabolic rate to maintain your body’s weight
    • Eating more doesn’t cause weight gain: it suppresses hunger and body will increase its metabolic rate to maintain your body’s weight
  • Increased appetite and decreased energy are not the cause of being overweight and obese. Becoming overweight is the cause of increased appetite and decreased energy.
  • The solution for most people who are overweight and obese is to decrease their insulin levels and reverse their insulin resistance
  • Due to leptin resistance in overweight and obese people, hunger doesn’t always mean the body needs fuel since normal leptin pathways aren’t working properly

We will talk about ways to decrease your insulin levels and your insulin resistance in future articles as part of our Lasting Weight Loss Series.  But if you want to read more about the hormonal obesity theory, it’s worth reviewing this series of articles and this one.    If you prefer to watch a lecture series, try this one.



El Camino Women’s Medical Group offers the latest Minimally Invasive Solutions for gynecologic problems.   Drs. Amy TengErika Balassiano, and Pooja Gupta, all members of AAGL (American Association of Gynecologic Laparoscopy) are highly trained and experienced in the field of Minimally Invasive Gynecologic Surgery.   Dr. Erika Balassiano has also completed a Minimally Invasive Gynecologic Surgery Fellowship, under the supervision of world-renowned Dr. Camran Nezhat.


Serving Mountain View, Los AltosLos Altos HillsAthertonPalo AltoRedwood CityBurlingameSaratogaCupertinoSunnyvale, Los GatosCampbellSan JoseSanta Clara, Silicon Valley, MilpitasFremont, South Bay, East Bay, and North Bay.