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Video Link “The Calorie Challenge”
A calorie is the most common term that people refer to when they are describing the content of food. Yet, it doesn’t provide much detail about food. Much less does it really serve as a useful tool to those who are working toward a healthier weight. In this post, I will describe the term calorie, how digestion involves multiple mechanisms, and how the calorie should be considered an outdated term.
What is a calorie? It is the amount of heat (in Joules) it takes to raise one 1kg of water 1 degree celsius *(Calorie). From the chemistry lab to the food that we purchase in the grocery stores, It was popularized in 1918 by a physician from California, Dr. Lulu Peters. It became the measuring stick of a daily diet, and the American Diabetes Association recommends approximately 2000 calories per day. The very common dogma growing up and still promoted is that weight gain occurs from eating an excess amount of calories than what is expended. There is no further information to what constitutes that unit of energy – is a calorie a calorie?
As a child growing up, I had challenges with my weight. It accumulated around my waist and then my it began to show on my face (I will include this in a later blog). I looked at this “calories in, calories out” model when I approached getting healthier as a teenager. I found myself going through a yo-yo course of eating less calories, hoping that I would lose weight and rebounding after eating a higher calorie count. I found myself only gaining more weight.
In fact, what I stumbled upon was a disconnect with the concept of calories in and calories out and what actually happens in the body. The term of a calorie may be one better left for the Bunsen burner of the chemistry lab than for food labels. The body handles each constituent differently, whether it is a carbohydrate, a protein or a fat. Unlike a certain amount of heat to break down the food, our bodies utilize multiple methods to digest, absorb and metabolize the food that becomes the building blocks of our body. What is broken down is stored in various forms to used in between meals or when an increase of energy is required, such as in exercise. The following will be a description of how our body uses the food we eat.
Digestion, Absorption and Metabolism in the Body: A brief, detailed overview
Starting with food entering the mouth, chewing it mechanically breaks down the food and exposes it to our saliva which coats the food for swallowing and starts breaking the starches (amylase in the saliva). When we swallow the food bolus (amount), the esophagus moves the food through contractions into our stomach.
Inside the stomach, the food is churned mechanically and also exposed to protons (acid) that help to break down the food further. There are proteins (enzymes known as proteases) in the stomach – trypsin and pepsin – which get a head start digesting the proteins into the amino acid components. In the duodenum, the first segment of the small intestines, literally translated as 12 finger breadths, the digesting food is met with multiple substances from the gallbladder, known as bile, which breaks down fat and cholesterol, and the pancreas which breaks down fats (lipase) proteins (trypsin and chymotrypsin) and carbohydrates (amylase) — and still others (elastace, ribonuclease, etc).
These breakdown products can then begin to enter the small intestines and make their way into the venous system (portal system) of the liver to become metabolized and detoxified by the liver tissue. This is the initial setting of glucose, protein and fat/cholesterol metabolism. A hormone secreted in the pancreas – insulin – helps to keep sugar at a balance in the bloodstream. Excess sugar seen in diabetes can become harmful in the vascular system. The pancreas adjusts the amount of insulin needed and secretes more insulin when more glucose is absorbed. Fatty acids which are derived from fats that we eat are converted with glucose in the liver into triacylglycerides (and transported in chylomicrons) from the blood into adipose tissues.
Insulin metabolism shifts the glucose into cells of muscle tissue, the brain and organs and shifts glucose in the form of triacylglycerol to complex in fat tissue (adipose tissue) and increase fat stores. The level of glucose in the blood is closely monitored by several hormones, insulin, glucagon and somatostatin, which keep the glucose at a basal (steady) requirement – in a non-eating state. The liver stores excess sugar by means of insulin into glycogen, which can buffer the blood glucose levels for up to 12 hours of fasting state. After these stores are expended, the adipose (fat) tissues of our organs, white adipose tissue (WAT) start being utilized by converting the triacylglycerates back into free fatty acids which are converted into ketone bodies in the liver — betahydroxybutyrate, acetoacetate, etc.
The body can use ketone bodies to derive energy. In some early ultra-low carbohydrate starvation studies, samples of blood taken from the carotid artery (the artery which goes circulates blood to the brain) found betahydroxybutyrate, suggesting that the brain can survive on ketone bodies in starvation states as well as glucose in surplus states.
There are also feedback systems for hunger. An empty stomach produces a hormone ghrelin which functions in the brain to trigger hunger and appetite. When the stomach expands, the ghrelin levels drop. Adipose tissue produces a hormone leptin which triggers satiety. With increasing obesity, ghrelin continues to function normally, but there is a state of leptin resistance. Ghrelin may have other effects on the brain, including mood, memory, and growth of new nerve cells that are beginning to be more understood.
What leads to obesity is more of a intake disequilibrium rather than a calorie equation. When sugars (complex carbohydrates are broken down to glucose in the gut) are more prevalent in the diet, the body metabolizes the absorbed glucose surplus leading to more being shifted into adipose tissue. Weight gain “simply” is a result of this imbalance of intake. I put quotes on “simply”, because if it were this simple, everyone would be able to normalize their weight. The added challenges include behavioral loops, taste memory and emotional eating as the glucose actuates (and even our gut microbiome! – stay tuned for a future blog on this) neurotransmitters in our brain that control our mood and memory.
Taking the above information and boiling it down (no pun intended), the message is that calorie counting, while it may be a tool to which we are all accustomed, doesn’t really help much to understand the more important concept of what we eat and how the body metabolizes that in a way that can lead to weight gain or weight loss. How many calories we eat, although a surrogate marker for how much we eat, doesn’t describe the individual components of fat, carbohydrates and protein along with fiber. There is more going on in our body than “burning food”. Furthermore, calorie counting for your exercise program is also fraught with problems because they generalize estimated calorie loss and they don’t take into account calories burned through respiration and resting metabolic rate (RMR). The concept of calorie misses the mark when it comes to describe the metabolism of food and the acquisition of energy in the resting and exercising body. It is as if we were using an archaic measurement and still applying it to things out of habit, rather than using other, more accurate tools.
Below are a few suggestions for working toward a healthy diet:
- Eat mostly plant products such as green,leafy vegetables and vegetable products such as legumes and to a lesser extent fruit. Green, leafy vegetables should be at the base of the food pyramid. It is replete in water, undigestible fiber and vitamins and minerals, which gives each vegetable its own color, aroma, texture and taste. Start every meal with the vegetable first – since this can be more fulling.
- Favor the original product over the processed product, e.g. steel-cut oats over granola, peanuts over peanut butter, etc. If it is boxed and capable of long storage, save that for your earthquake-ready food kit (for all of those who live in the NW or other earthquake prone areas) rather than the first go-to food in your pantry.
- Avoid liquid sugars, favoring water as the only source of hydration. These liquids include juice, soda and milk. Favor the original source, e.g. orange instead of orange juice.
- Ditch the calorie counting — I say this understanding that many people have been doing this for a long time and feel like it offers some control. Unfortunately, it tells us little about of how wholesome a food is. We also tend to underestimate the calories in the food we eat. It might give us a false security that a certain number is going to be a target for possible weight loss, and often leads to the up and down cycles of intake. If you would like to count something, you could try carbohydrate counting. But – just as a calorie is not a calorie, a carb is not a carb. A good rule to follow is to eat real food. Also, ditch the calorie counting for exercise. Our body, while it generates heat, doesn’t burn calories in the strict sense – it utilizes tissue glucose to make the needed adenosine tri-phosphate (ATP) at the cellular level for the increased activity. When this occurs, there is Not some magical calorie deficit — there is just hunger. Don’t ditch the exercise though — do that every day!
I hope you enjoyed reading this post. Remember little changes over time can lead to big results. It really is not a sacrifice at all to lose weight — it is a discipline that strengthens over time – even in someone who failed every diet before the last diet I every needed to go on. I sometimes hear patients exclaim, “but doctor, these (sweets) are the last pleasures that I have!” I recount to them that when I was younger I rarely used to eat salad, but after finding a way to make it taste better to me (I use a little olive oil and salt), I now eat three plates of salads every day. Well, after doing this for nearly 15 years, I have come to find pleasure in the variety of natural foods and their preparation. They are truly multi-dimensional foods.
Stay tuned for a future blog that details my personal journey toward finding health.
For additional reading on the topic of calorie, I would recommend Dr. Zoe Harcombe’s book The Obesity Epidemic and Gary Taubes’ book Why we get Fat and what to do about it.