Does the human body run better on fat or sugar? This question is probably too simple since there are many factors involved in how the body processes fuel. For instance, personal preference, individual health goals and activity levels may play a role. However, for the purposes of this blog, I just want to outline some basic principles and talk about fat burning vs. sugar burning.
Fat Burning Vs. Sugar Burning
When the body burns sugar (glucose), it gets its fuel source from carbohydrates. Carbohydrate sources are foods like refined sugar, fruits, bread, pasta, cereals, grains, starchy vegetables and a myriad of processed foods. When we eat carbohydrate, it goes into the body and is transformed into glucose in the bloodstream. Our pancreas then gets a signal from the body to produce a hormone called insulin. It is insulin’s job to push glucose into the cells so that the body can then use that glucose for fuel.
How high your blood sugar spikes is a result of how your body processes a particular carbohydrate as well as how sensitive or effective your insulin is at pushing glucose into your cells. This can vary among individuals depending on genetics, gut bacteria, metabolic health, etc… Insulin suppresses fat-burning so it is also known as a fat-storage hormone. If you are running insulin all day to deal with glucose, you will store more fat. This can also be affected by activity level, so you can also be lean and be in a state of steady insulin production. However, for most people they will store more fat.
When the body burns fat, the story looks quite different. In the context of low carbohydrate consumption, the hormone insulin goes quiet. As a result, a different hormone called glucagon is manufactured by the pancreas. Glucagon signals the body to release fat stores and burn it as fuel. The result is quite interesting. The body will lose fat stores easily and will shift into a mode of fat-burning. However, this shift from glucose-burning to fat-burning can be uncomfortable for some people if they are not used to a low-carbohydrate diet. They might first experience the effects of a dip in blood sugar because the body is not yet efficient at fat-burning. This can give you typical low blood sugar symptoms like extreme cravings, shakiness, moodiness, tiredness, or what is colloquially known as “hangry”. This makes going from sugar-burning to fat-burning a little difficult for many people, but it can also be effectively mitigated if you plan meals correctly.
Your Body Is Like A Hybrid Car
Like a hybrid car, the human body is built to run on these two fuel sources- fat and glucose (sugar). Throughout history, most people fluctuated between a fat-burning and glucose burning state since there were periods of time with low carbohydrate or low food availability. Therefore, it is natural for the body to cycle in and out of a fat-burning state. We call this “metabolic flexibility”. Most ancient humans relied on metabolic flexibility because they could not be disabled by a state of low blood sugar. In fact, they likely did not experience being “hangry” as often or quite as regularly as modern people since they could seamlessly transition into fat-burning since carbs were simply not always around.
The problem is, in modern days, most people are burning glucose for fuel all day long because they are consistently eating every few hours. Also, most meals contain carbohydrate. They get a dip in blood sugar and hunger occurs, so they eat more glucose containing foods (fruit, bread, pasta). This keeps the body in a constant state of glucose dependence with a constant stream of insulin production to deal with the glucose as well as a constant state of fat storage.
Burning Sugar: It Makes You Hungry And It Makes You Fat
Since most people who are glucose dependent have multiple dips in blood sugar throughout the day, they need to eat shortly after they wake up and every 3-4 hours throughout the day. They also spend a lot of time having to look for food throughout the day. They often cannot stop eating 3 hours before bedtime and will eat right before bed. In this scenario, they may have signs of fomenting insulin resistance like abdominal obesity or they are generally overweight.
Sugar burning all day is like burning fuel in one half of the hybrid engine all day. Over time it puts a burden on one part of the machinery and eventually, that part of the system wears down and no longer works very well. One way the system begins to shut down is when the body exhibits symptoms of insulin resistance and eventually, diabetes.
Diabetes: The End of the Insulin Line
The pre-diabetic and diabetic state is when insulin receptors stop working and glucose is not being pushed into cells efficiently. This causes an increase in blood glucose or blood sugar. Most conventional doctors focus on blood sugar when it gets out of control. They may send you for a fasting blood sugar test to see if sugar is still floating around in your bloodstream after 12+ hours of no eating. If blood sugar is still high, you are diagnosed with either pre-diabetes (100-125 mg/dL) or diabetes (over 125 mg/dL).
The fact is, the damage is already being done before blood sugar levels increase to clear pathological levels. I believe that we need to focus on the state of hyperinsulinemia (high insulin) before glucose increases on a fasting blood test. Are you running insulin all day because you are eating carbs at every meal? Does your body (and brain) ever get a break from running on one fuel source all day? Are you slowly becoming insulin resistant and don’t even know it because your blood sugar appears “normal”?
Without metabolic flexibility (fat burning), we run on one engine all day (glucose) and over time we become inflamed and run the risk of autoimmune flare-ups and cardiovascular disease. There are studies that show that the state of insulin resistance is highly correlated with some types of autoimmunity, psoriasis and rheumatoid arthritis in particular. The state of diabetes is the most overtly obvious pathological state of insulin resistance. However, this process starts much earlier with hyperinsulinemia and the constant stress of the carbohydrate-insulin-glucose cycle.
In order to reset the immune system and to stay insulin sensitive, we need to help the body out by reducing glucose consumption overall. We do this by reducing fruit, fruit sugar (juice), pasta, bread, and basically all foods that increase blood glucose and thus increase insulin production.
Once we get out of a constant state of glucose dependence, hunger cravings abate and we can go longer periods of time without eating. Our bodies become more effective and efficient at fat-burning and we feel healthier. We start to slim down, we have more mental clarity. We are in a state of metabolically flexible and less prone to disease. We can eat carbs intermittently or cyclically and we will not be burdened by glucose dependence.
There are several methods of getting into a fat-burning state.
Low Carb Diets
These are diets that consist of high-quality proteins, high-quality fats and low carbohydrate foods like above-ground vegetables. There is a variety of ways to do a low carb diet. A good start is a whole foods ancestral or paleo diet that is low in starchy vegetables.
These are diets that consist of high-fat, moderate-to-high amounts of protein along with very low carbohydrate (about 50 grams per/day). I recommend anyone who is glucose-dependent to first do a simple low-carb diet and later ease into a keto diet for a period of time and see how they respond. It is important to note that there are many ways to do a ketogenic diet (cycling keto, full-time keto, etc..). There are also many ways to do a keto diet wrong.
It is best to consult a trusted health care provider who truly understands keto. If your doctor tells you that you are at risk for ketoacidosis by doing a ketogenic diet, and you are not a type 1 diabetic or severe type 2 diabetic, you need to walk in the other direction and that doctor needs to review their basic biochemistry and pathophysiology. If your doctor tells you that a ketogenic diet may increase risk for kidney stones, this could be true. However, there are ways to mitigate the risk and still do keto. If your doctor tells you that keto will drive up blood cholesterol, this could also be true. However, this is only for about 20% of people who do keto and this can also be mitigated dramatically by cutting foods that are very high in saturated fats, namely dairy and coconut oil. In my clinic, when we have patients who want to adhere to a keto or high-fat diet as a lifestyle intervention, we do an advanced fractionated lipid panel with fasting glucose and inflammatory markers every 3-4 months for the first year. We want to know how your body responds and then modify things as needed.
When done correctly, there are many amazing benefits of being in a ketogenic state of pure fat-burning. People report dramatic increases in mental clarity, decreased hunger and an overall sense of well-being. Ketogenic diets are used as a therapeutic tool for people with brain injury, cancer, Alzheimer’s and seizures. This is because the state of ketogenesis has neuroprotective and healing effects for many people.
A lot of people say that doing keto is very hard and not sustainable. My response to that is it depends on how you do it. Some people love being in keto all the time, while others like to do more of a cyclic version of keto where they may spend Mon-Friday doing keto and take weekends off. There is a myriad of versions and endless food preparation options. In my clinic we work toward doing what is best for you and supporting you in making changes. We even offer personal chef services and meal planning for those who really want to dive in.
Most people will go into a mild state of fat-burning during intermittent times of food restriction. Fasting is a natural state for the human body since for most of human history there were times of food scarcity. In a nutshell, our bodies are not only built to fast but our bodies also go into repair mode when in a fasted state.
There are several ways to fast. Intermittent fasting is usually where people start their fasting journey. This is when you limit the time you eat during the day. For example, you could stop eating at 6pm and then don’t eat until 8am the next day. This way you have fasted 14 hours. Your eating window is then from 8am-6pm (10 hours). There are a variety of ways to do this and you can play with times and eating windows. Some people compress their eating window into 8, 6 or even just 4 hours per/day. What you do depends on your goals and how you can practically fit intermittent fasting into your daily life.
Another way of fasting is to just not eat food and only drink water for 24 hours. Some people do this once or twice a week and turn up the volume on fat-burning and thus experience weight loss. This is when you might eat dinner one evening at 6pm and then not eat until 6pm the following day. Again, this is harder for glucose burners because they may experience blood sugar instability. For fat-burners or what we call individuals who are “fat-adapted” it will be much easier since hunger pangs are less intense while fat-adapted. This is why I only recommend fasting for people who have developed some level of metabolic flexibility.
Fasting is an advanced method of flexing your metabolic muscle. Again, I do not recommend that glucose-dependent individuals jump into fasting. I recommend adapting to at least a low-carb diet first for 30 days and then try some intermittent fasting. From there it is safer and easier to expand fasting times.
If you have more questions about anything related to fat burning, sugar burning, low-carb, ketogenic diets or fasting please make an appointment here for a personalized nutrition consultation today. We specialize in getting people into a program that suits their health goals, preferences and lifestyle.
If you are also suffering from complex issues, we also specialize in functional medicine consultations which include personalized nutrition protocols along with more in-depth investigative work that includes more extensive lab testing. Whatever option you choose, your individual needs and goals will be heard and we will work together to figure out the best path for you!