hypothalamus appetite

Low Carb Diets, Appetite, and Weight Loss: the Basics

February 24, 2017

“Tell me what you eat, and I will tell you what you are.”
-- Jean Anthelme Brillat-Savarin

It’s obvious to anyone who has ever been obese that what we eat matters greatly.  What is not as obvious are the subtle effects that our choices can have on the body or the mind. It’s difficult to lose weight and anyone who has undergone weight loss surgery knows that it is not merely a matter of willpower--it may be a part of the equation, but if it were the only factor none of us would probably have gained weight!  Many of us have overcome this using lower carbohydrate diets. In fact, if you talk to weight loss surgery patients, it’s clear that a majority who are successful eat this way long-term.

But why are low carb diets in particular so effective for us?   No one ever seems to explain this, and nutritionists, as all weight loss surgery patients know, have a huge variation in the advice they offer to us. Having studied much biochemistry and neuroscience, this prompted me to explore the issue myself. I also discovered that my appetite was far more regulated when I was super-super-morbidly obese when I ate low carb than when I followed the standard American diet (SAD) recommendations. For the purposes of the current discussion, we will not address malabsorptive procedures such as the DS (which has a unique high protein and fat requirement besides) but simply the low carb and appetite basics.  This made me very curious and prompted me to investigate. I put my early background in biochemistry to good use.

The answer to this question I found myself asking many years ago is a bit complicated, and it involves the brain. Hunger and appetite are complicated things and extend far beyond our stomachs.  We often tout surgeries for reducing our level of ghrelin, the infamous “hunger hormone,” but in truth, a fair bit contributes more than that, and it all starts with what’s upstairs.

Hypothalamus, the Appetite Regulator

It all starts with a structure in the brain called the hypothalamus. This tiny structure acts as a link between our nervous system, our brain and nerves, and our endocrine system. It regulates appetite via a complex system that involves many hormones: glucagon, insulin, ghrelin, and leptin, among others.

You may already be familiar with the endocrine system as our reproductive glands (ovaries or testes) are a part of it. What you may not know is that the endocrine system is involved in regulating appetite, and the hormones that are secreted can vary based on—you guessed it!—what we choose to eat. Obesity can be understood then to be a result of many factors.

One significant factor, often overlooked, is the hormones that are released when we eat certain kinds of food. Low carbohydrate diets encourage weight loss, even independently of caloric restriction to some degree, because of this.

It all comes down to energy sources.  The body is designed to be efficient.  It will utilize one of two main sources of energy depending on which is available: glucose or fat.  Depending on your glucose intake, the production of insulin or glucagon is stimulated.  This is because fat and glucose are used differently in the body, and require separate pathways to process.  Why do we care about those two hormones after weight loss?  And what the heck do they have to do with the brain?

The Importance of Insulin

Insulin, for instance, is actually a neuroendocrine hormone.  Insulin is important - it exists, so we do not die. Without insulin, we would waste away into nothing, because the body requires insulin to process, not only carbohydrate but also protein, as well.  While insulin lowers blood sugar so it does not reach a dangerous concentration, another hormone known as glucagon raises blood sugar when glucose decreases. This is because some tissues in the body are dependent on glucose, and some will use glucose preferentially even though they can also use fat. Insulin is key in the process of breaking down protein and carbohydrate into this fuel.  It is the gatekeeper that allows cells to grab glucose as it drives past in our bloodstream, and normally this system functions efficiently and without errors.

Problems begin to evolve when excess insulin floods the body.  It can cause systemic inflammation, and it also causes something we who have been obese are familiar with - a state called insulin resistance. This is believed to be primarily caused almost entirely by eating too many carbohydrates and having raised serum insulin, for an extended period of time - even decades.  When they are overexposed to insulin, cells appear to lose much of their ability to utilize glucose normally.

They send a note to your brain using hunger hormones that make you hungry, even if you just ate. This is one of many reasons why, as many of us have noticed post weight loss surgery, it is all too easy to eat processed carbs and we desire to eat dense protein far less.

Eating huge amounts of carbohydrate makes this cycle spiral downward.  Eventually, this begins to affect the pancreas which becomes overburdened and can’t keep up with demand.  The cells become damaged, and you become pre-diabetic.

Low Carb Diets

After pre-diabetes, type 2 diabetes develops. The good news is that even if you are genetically predisposed to obesity and type 2 diabetes, food choice can go a long way towards preventing them. Additionally, fat storage is directly activated by insulin—restricting it provides further benefits in this vein, as well.

Low carb diets provide a method of safe glucose control which is the primary benefit for those who have diabetes—which many pre-operative weight loss surgery patients are. Not eating sugar and starch allows the liver to produce glucose on demand from glycogen, and this allows an individual to potentially maintain a safe range of glucose when they have been unable to previously. This is huge, especially in addition to the help managing appetite.

The importance of eating correct macronutrients can’t be overstated, especially for the obese and formerly obese. Also, insulin is a powerful appetite stimulant, you see. It affects the proportion of leptin and ghrelin - two other neuroendocrine hormones that regulate appetite. We were taught in school that ghrelin increases appetite and leptin decreases it. Weight loss surgery also reduces serum ghrelin for reasons that are incompletely understood. A natural way to keep ghrelin low regardless of surgery is to eat a diet higher in fat and protein than in carbohydrates. This encourages leptin production and results in a more regulated, and less haphazard sense of appetite. There are further benefits to eating low carbohydrate to the point of remaining in a nutritional state known as ketosis (not to be confused with ketoacidosis), however, that is a whole other tangent!

Who knew that food was so powerful?  We truly can become what we eat to our benefit or detriment.


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Donna Lordi, MA, is a counselor in the state of Illinois. Donna graduated from Lewis University with a Master’s in Counseling Psychology, and she has additional certification in working with children and adolescents.  Donna is also a contributing author for the book Hooking Up: The Psychology of Sex and Dating by Dr. Katherine Helm, PhD.

Read more articles from Donna!