You guys do ask some very thought-provoking questions. The question on sugar got me thinking……can you burn fat if all you eat is sugar?
Lipolysis – the breakdown of fat stores
First, let’s talk about what process the body goes through when we eat. When your energy needs increase or your blood glucose level fall, the production of hormones that mobilize your energy stores begins to rise. These hormones -- such as glucagon and adrenalin -- stimulate lipolysis, which involves the breakdown of triglycerides stored in your fat tissue. The fatty acids and glycerol molecules liberated by lipolysis are then metabolized to generate energy to meet your needs. The hormones that oppose insulin and stimulate lipolysis are called glucose counter-regulatory hormones. So again, it is not all or none when it comes to blood glucose levels. It is more of a checks and balances system where when insulin starts to fall, glucagon, adrenalin, ghrelin, even hGH levels start to rise, leptin levels fall. When insulin levels start to rise glucagon, adrenalin, ghrelin and hGH start to fall while leptin starts to rise. This is a very complicated system and certainly not limited to these hormones as we have not even disccussed satiety/hunger or micronutrients involved in the production of these hormones. Further more, both adipocytokines and thyroid hormone may be affected by energy balance and body weight.
Here is zomething to keep in mindin this process and in fasting…….as blood sugar levels fall glucagon and adrenalin rise along with hGH. This protects the body against muscle loss during starvation and also give you a boost of energy in hopes if finding more food.
What is Insulin?
Insulin is secreted from pancreatic cells in response to rising levels of glucose in your bloodstream. The consumption of food -- particularly proteins and carbohydrates -- prompts the release of insulin from your pancreas. Note I did say proteins? Which is why a ketogenic diet is not high in protein. In fact, a well done keto diet consists of 20% of your total calories or less protein or 1.2 - 2g/kg. Excesses will go through gluconeogenesis to produce glucose kicking you out of ketosis. Now granted this process takes a little more time and more energy but excesses still get turned to glucose and stored as body fat.
So in short, carbohydrates are meant to provide the human body with an immediate source of energy for work. When we eat lots of carbs and sit on our ass doing nothing, this energy is then stored as fat. There lies the problem the world has with rising obesity and diabetes. We are eating enough carbs to provide the energy or a highly trained athlete but sitting on our ass playing video games.
Back to sugar…..sugar is called sucrose and is a disaccharide, a molecule composed of two monosaccharides. Because of the very short chemical chain it is broken down very quickly and absorbed in the blood very quickly. This causes a rapid rise in insulin which quickly clears the sugar from the blood and then there is a very rapid decrease in insulin. The whole process takes from mouth to blood around 30 minutes. So, unless you have a continuous feed of sugar 24/7 you are still going to quickly enter a fasted phase where blood sugar drops, glucagon, adrenalin ghrelin and hGH rise causing the body to once again oxidize fat stores for energy. So, can eating sugar cause lipolysis to shut down? It all depends on how frequently you eat sugar and how much energy you take in from eating sugar. Once the body is low on energy, it always breaks down stores to provide the energy.
Just a note on Dr Fung. He seems to be very basic on his information and explains things is a very simple way. Good information for the most part, but a "EXPERT" he is not. My wife has been listening to this guy for a few years.
A good post Tex. Thank you for posting it. It’s useful for all readers.
A couple comments; carbs (not simply glucose / “simple carbs”) come in many forms — some natural and others anything but natural. ALL carbs (dextrose, sucrose, fructose, etc….) go through various conversion processes eventually making glucose. The various substrates have differing actions though.
Far more in-depth than “simple carbs” and “complex carbs.” And far more in-depth than simply low and high glycemic.
The amount and rate at which insulin rises and falls varies RADICALLY!
And in the state of health (lack of health) that most Americans are in; insulin resistant / pre-diabetic and diabetic, along with the common frequency of consumption from morning into evening — insulin levels seldom drop into a normal range for the avg American.
Also, ancestrally, carbs aren’t much of a species appropriate macro. They aren’t common in nature (basically they weren’t globally available, and they were seasonal). What is common are fats (most abundantly saturated) and protein.
Being that carbs are technically a non-essential macro nutrient —non essential because we don’t have to exogenously ingest them to produce our body’s minimum need (because of processes like gluconeogenesis), an animal based diet (example: beef, fish, organs) is the most natural / species appropriate way of nourishment.
Excessive carb consumption came about only in fairly recent history. To the extent (and types) consumed, it’s highly unnatural.
So far as Fung as an “expert,” in a certain respect he is. He’s a nephrologist (as you’re aware) treating metabolic conditions daily in his practice, primarily via nutrition. Has written books on diet and nutrition and fasting, and a diligent researcher of nutrition and metabolic studies, etc. He qualifies as an “expert” of sorts.
Carbs can be / are a tool for various specific uses, but their consumption isn’t optimal for overall health. Sports supplements are another example of the same principle; effective as tools for various goals / uses, but not a true natural contributor to overall health.
Sorry for misspellings / grammar mistakes. Typing thoughts quickly on my phone between sets at gym!