“The rise of childhood obesity has placed the health of an entire generation at risk.” ~Tom Vilsack
Often of late, we hear non-experts make sweeping pronouncements on subjects from healthcare and education to socioeconomics. Seldom do they add anything to the conversation, instead muddying the already perturbed waters. While we certainly cannot fault someone for proffering an opinion, however, we must remember that they are no more than an opinion, or an idea.
Of course, some ideas are more lasting than others, and on rare occasions, these facts have held up to rigorous scientific scrutiny. An example is the Theory of Evolution. It should be noted that the term “theory” used in science means a well-substantiated explanation of the natural world; one based on facts repeatedly confirmed by observation and experiment. This explanation seems to confuse some people, and others, being intellectually dishonest, attempt to imply that a scientific theory is simply a guess. Therefore, it seems that some explanation is needed to outline the steps in the scientific method: Observation, Hypothesis, Experiment, Analyses of Data, Draw Conclusion.
Observation and Hypothesis
A hypothesis is a reasonable guess, based on knowledge or observation, as to how something occurs, or, more frequently, how one variable might effect another (if at all). For example, one hypothesis put forward in the 1970’s was that for many people, the regular use of tobacco products resulted in Cancer of the lungs. The original question may have been something like “Why have medical practitioners seen a drastic increase in lung cancers in the past 20 years.”
After formulating a series of research questions based on observation, the researcher creates a Hypothesis and a Research Question (RQ) that will attempt to address the original question. They then make a testable prediction, test, and then analyze the resulting data. The hypothesis will need to be tested, retested, and tested again before it is accepted as being true.
The research question may have looked like this: Is there a statistically significant association between subjects who smoke tobacco and the development of lung cancer. The RQ was simply a hypothesis (a pretty good one if we are honest). However, hypotheses are proven and disproven all of the time. The use of hypotheses is critical in the scientific method.
A scientific theory consists of hypotheses that, after repeated testing, have been shown to be true, at least thus far. Theories in science are one of the pinnacles of provability because the theory must never be shown to have been wrong in its prediction. Scientific theories can and do evolve; this is not indicative that the original theory was incorrect, just incomplete. An example is Newton’s theory of gravity. While Newton could show what gravity did, he did not fully understand why it did it.
Scientific laws are short, sweet, and always true. They are often expressed in a single statement and rely on a concise mathematical equation. Laws are accepted as being universally true, and are the cornerstones of science. They must never be wrong (that is why there are many theories and few laws). If a law were ever to be shown false, any science built on that law would also be wrong. For example, E=MC2 has been shown to be true, at least thus far; however, it is not in itself a law, but a central tenet of the Theory of Special Relativity. It is not inconceivable (although the odds are astronomical against) that all space is not the same.
Examples of scientific laws include one of the simplest, yet frequently misunderstood laws, Thermodynamics. Thermodynamics involves the properties of temperature, energy, and entropy. Boyle’s law describes how the pressure of gas increases as the volume of the container decreases, in other words, the force exerted on the container by the compressed gas. Both of these laws can be shown to be true mathematically. While scientific laws describe a formula that explains what will occur, they may not always describe why it will occur. A good example is the Law of Gravity.
According to Sir Isaac Newton’s Law of Universal Gravity, “Every point mass attracts every single point mass by force pointing along the line intersecting both points. The force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between the point masses.” What this means in plain language is quite a bit simpler: gravitational force is inversely proportional to the square of the separation distance between any interacting objects, the greater the separation distance, the weaker the gravitational forces will exist between them. As two objects are separated from each other, the force of gravitational attraction between them also decreases (Inverse square law). This law accurately predicts what will happen, however, not why. Is gravity simply a result of mass warping space-time as described by Einstein? Is it the result of gravitons (a hypothetical that mediates the force of gravitation in the framework of quantum field theory)? You see how a law explains the what, but not the how (the how is in the theory, which of course begins with a question and, you guessed, a hypothesis).
One theory (which many accept as law) is that obesity is caused by overeating. While a poor diet and large quantities of food poor in nutritional value may lead to overeating, the fact is obesity is a very complex interplay that involves energy consumption, energy expenditure, hormone production, activity, resting metabolic rate, dietary intake, and several other factors including the type of fat a person has and how much of it. But as health science has come to realize, fat is not just fat and obesity has complex causes.
The human body has two major types of fat tissue: white fat and brown fat. In the human body, fat is used for energy, the maintaining of body temperature, regulating hormones, and as a store of energy for later use.
White fat is found around the kidneys and under the skin in the buttocks, thighs, and abdomen and is used to store energy, manufacture and store hormones that control appetite and hunger, and helps regulate appetite. Comprised on a single lipid, white fat has significantly fewer blood vessels (explaining why it appears white), and it is the main form of fat in the body, created from connective tissue. Because white fat is critical in the creation of estrogen, adiponectin, and leptin (hormones that help regulate hunger including leptin), it is a major endocrine gland. White fat also has numerous receptors for glucocorticoids, growth hormones, and important stress hormones including adrenalin, norepinephrine, and cortisol. Finally, white fat also produces inflammatory substances, as adipocytes of obese individuals tend to attract macrophages (part of the immune response), promoting inflammation, and increasing the release of inflammatory factors that influence insulin resistance. In obese persons, large numbers of immune cells infiltrate adipose tissue, promoting a low-grade chronic inflammation, which has been associated with hypertension, heart disease, and metabolic syndrome. Because white fat acts as an endocrine organ, it seeks self preservation. If it begins to disappear through diet or exercise, it can suppress the release leptin (which tells the hypothalamus to instruct us to stop eating), tricking us into believing we are still hungry.
Brown fat is found on the upper back of healthy human infants and adults. Brown fat (also known as the good fat) releases stored energy as heat when we are cold. However, it also produces some inflammatory chemicals. As you can see, all fat is the same, and there can be many reasons why people are overweight or obese, including some medical conditions that make it very difficult, if not impossible, to reduce the amount of fat we have, or to alter the balance of white fat to brown fat.
Medical conditions that are well known to cause or to complicate overweight or obesity include some genetic syndromes and endocrine disorders (remember, white fat is an endocrine organ). The most prevalent of these include Prader-Willi Syndrome, a genetic disorder caused by the loss of function of specific genes. Prader-Willi Syndrome causes weak muscles, poor feeding, and slow development in infants, yet causes young children to be constantly hungry, often leading to obesity and type 2 diabetes. Because the endocrine system produces hormones that are critical in maintaining the balance of energy in the body, endocrine disorders can cause overweight and obesity.
Hypothyroidism. People with this condition have low levels of thyroid hormones. Thyroid hormones, in particular, triiodothyronine (T3) and its prohormone, thyroxine (T4). T3 and T4 affect nearly every physiological process in the body, including metabolism, body temperature, and heart rate. These tyrosine-based hormones are produced by the thyroid gland, and underproduction (hypothyroidism) significantly slows metabolism. For people with hypothyroidism, even drastic reductions in caloric intake are insufficient to normalize weight. People with hypothyroidism also have difficulty producing body heat, and as a result, have a lower body temperature, and are unable to use stored fat efficiently as energy.
Cushing’s Syndrome. People suffering from Cushing’s have high levels of glucocorticoids, including cortisol, in their blood. Abnormally high cortisol levels trick the body into thinking it is under constant stress. As a result, people have an increase in appetite and the body will store more fat. The symptoms of Cushing’s can include high blood pressure, abdominal obesity (Apple shape) but with thin arms and legs, often with a round face. Cushing’s can develop after taking some medicines, or if the body manufactures too much cortisol.
Type-2 Diabetes. In healthy individuals, insulin released from the pancreas activates glucose uptake in peripheral organs. Insulin is activated by the rise in postprandial (after eating) rise in blood glucose. Insulin promotes increased glycolysis and respiration and enables the storage of glucose and lipids through the stimulation of glycogenesis (glucose is added to glycogen), lipogenesis (acetyl-CoA is converted to fatty acids), and protein synthesis (generating new proteins). Insulin also reduces degradation and recirculation of carbohydrates and lipids by inhibiting gluconeogenesis (forming glucose from non-sugars) and lipolysis (breakdown of lipids). The causes associated with Type-2 diabetes are complicated and include a number of preconditions including genetics, life style, diet, and family history.
Tumors. There are some tumors, such as craniopharyngioma (a type of brain tumor derived from pituitary gland embryonic tissue), that occurs most commonly in children, can also cause severe obesity, because the tumor grows near or invades the part of the brain that helps regulate hunger.
Medicines. There is a host of medications that can cause weight gain, and may lead to obesity. Medicines such as antipsychotics, antidepressants, antiepileptics (used to treat epilepsy), and antihyperglycemics (used to lower blood glucose) can cause weight gain, which can lead to weight gain and obesity.
Abnormal Microbiome. As previously discussed, obesity has been characterized as an imbalance between energy intake and energy expenditure and involves a complex process that involves genetic, biological, and environmental factors. One area that has attracted renewed interest is the Microbiome, or as it is commonly called, the “Gut Biome.” The human digestive track contains over 100 trillion microbial cells. These calls have the essential role of digesting food, processing and extracting energy from digesting material, and regulating metabolism. When this microenvironment is altered, through poor diet, medications, or the introduction of chemicals (pesticides, herbicides, improper foods) the microbial ecosystem fails to function properly. Scientists have researched how the introductions of unhealthy feed, residue from pesticides or herbicides, have been associated with increased metabolic and immune disorders in animals. In humans, the molecular interactions linking this microbiome with host energy metabolism, fat accumulation, and disruptions to immune response have been identified.
When you see someone who is overweight or obese, before you conclude they overeat and have a poor diet, remember, things are seldom as simple as they first appear.