Obesity and as a consequence chronic disease are two of the largest healthcare issues plaguing the U.S. currently. 42.4% of all U.S. adults are obese (>=30 BMI), and 19.3% of children are as well. These rates have been generally rising over time, increasing from 30.5% in 2000 to the current 42.4% number in adults aged 20+ (1). Chronic diseases, or diseases that persist past three months or get worse over time, such as heart disease, diabetes, cancer and hypertension also now affect a large number of Americans, with there being an estimated minimum of 129 million Americans suffering from at least one major chronic illness, although this number varies across sources (2). Similar to obesity rates, chronic disease rates have consistently increased over time (3). Multiple studies from other populations such as Australia and Saudi Arabia using longitudinal methods found a high degree of association between obesity and chronic diseases such as type 2 diabetes, hypertension, arthritis, depression and heart disease (3,4).
This situation has a clear widespread impact on the health of the American people. Multiple of these chronic illnesses are leading causes of death in the U.S. Heart disease is the leading cause, cancer follows in second, while chronic lower respiratory diseases, alzheimer’s, diabetes, kidney disease, and liver disease follow as the sixth through tenth leading causes (5). One 2023 study assessed the relationship between obesity and all-cause mortality and found that “The risk of all-cause mortality was elevated by 21–108% among participants with BMI ≥30” (6). Given that the chronic illnesses listed as leading causes of death above make up approximately 66% of all U.S. deaths (7), it would be reasonable to conclude that these two studies combined demonstrate another relationship between obesity and chronic disease. However, the study assessing the relationship between obesity and all cause mortality did note that it could not be fully concluded that obesity was an independent risk factor, so further studies and analysis are needed to draw definitive conclusions.
Not only does high rates of chronic disease pose major implications on U.S. national health, it has a heavy financial burden on the U.S. healthcare system. $4050000000 are spent annually on health care for people with chronic or mental health conditions (8). Overall healthcare costs have risen in the U.S. over time (with fluctuations surrounding the Covid-19 pandemic), coinciding with increased obesity and chronic disease rates from previous figures (9).
As with any major national issue, healthcare or otherwise, there has been significant research into reducing obesity and chronic illness. Recently, researchers have looked into lifestyle factors such as diet, sleep and exercise as a preventative and symptom reducing measure for major chronic illnesses (10,11).
Recent studies suggest that any combination of the Mediterranean, DASH, and plant based diets reduce the risk for cardiovascular disease and promote overall heart health (12). The Mediterranean diet promotes consumption of nuts, legumes, olive oil, and fatty fish which are all sources of poly/mono unsaturated fats. The DASH diet helps regulate salt consumption, lowering the risk of hypertension- a risk factor for heart disease (13). A plant based diet simply promotes lowered animal product consumption and high quantities of fruits and vegetables. The Mediterranean and DASH diets are subunits of the plant-based diet. Studies have also found such diets to reduce the risk for type 2 diabetes (18). Although a diet high in fruits and vegetables, and healthy fats from fish, olive oil and other sources is the most optimal method for reducing heart disease and diabetes risk, any diet that would create a caloric deficit and thereby promote fat loss which would reduce risk for heart disease and diabetes. In fact, a Tennessee man named Kevin Maginnis lost twenty-one pounds while eating only Mcdonald’s for a month. Not only did he lose weight though, he also improved markers for cardiovascular health such as reducing his LDL cholesterol (14).
Other less supported, opposing diet movements have recently arisen to claim the benefits of reduced chronic illness as well. Notably the ketogenic- a low carb diet composed mostly of fat- and carnivore- a meat, egg and dairy based diet.
Major proponent of the carnivore diet, Paul Saladino, MD, claims in his book The Carnivore Code that a carnivorous diet is the optimal diet for humans and provides anecdotal evidence of how it helped him clear up autoimmune conditions such as eczema. He also claims that in insulin healthy individuals, LDL cholesterol is not a risk factor for cardiovascular illness and is open in admitting his “elevated” levels of LDL cholesterol at around 130. Despite this and Saladino’s other anthropological evidence to support his backing of a carnivorous diet, current research continues to demonstrate LDL cholesterol is a risk factor for cardiovascular illness and consequently, “Dietary reliance on animal-based foods tends to increase numerous pathological molecular drivers of CVD” (15). Additionally, there is minimal evidence to support Saladino’s claims that a carnivorous diet can help mitigate the symptoms of other chronic illnesses outside of his anecdotes, and it is a possibility his anecdotes and others like it result from the consequences of an limiting overall consumption of processed, inflammatory foods rather than specifically adhering to animal products.
As for the ketogenic diet, most studies find overall inconclusive results regarding the diet’s ability to reduce and prevent symptoms of chronic illness (16, 12).
Another important lifestyle factor, exercise, has been found to minimize mortality and symptoms and serve as a preventative measure for cardiovascular disease and other chronic illnesses. A 2019 systemic review found that “lack of exercise leads to 6% of coronary heart disease occurrence worldwide”. Additionally, the paper cited a study with patients on statins (a medicine administered to those with heart disease to lower LDL cholesterol) that concluded “the risk of mortality is significantly reduced by combining statins with exercise, especially compared to other therapy alone”. Lower serum (blood) levels of LDL cholesterol were also found in rats post-exercise, however these results were not consistently demonstrated in humans and therefore are inconclusive. Exercise was also found to have positive effects on blood pressure, with there being significant reductions in both systolic and diastolic blood pressure. These reductions were significant enough that they “leads to 6% reduction of stroke mortality and 4% reduction of coronary heart disease mortality, and a decrease of 5 mmHg causes the reduction of mortality of these diseases by 14% and 9%, respectively”. For diabetes, both anaerobic (without oxygen) and aerobic (with oxygen) exercise was found to improve glucose control and insulin resistance due to its ability to “stimulates the translocation of glucose transporter type 4 (GLUT4) from the cytoplasm to the cell membrane, thus promoting glucose uptake” (17).
A common negative lifestyle factor that has been shown to increase the risk of obesity and chronic illness is alcohol consumption. The most prominent chronic diseases alcohol is a risk factor are liver conditions. A 2023 study retrospectively examining the Korean health database found that increased alcohol consumption raised the risk for liver related diseases (19). Alcohol is naturally toxic to the body and must be broken down in the liver, the liver breaks alcohol down into acetaldehyde, a carcinogen which can lead to tissue damage and the formation of free radicals, potentially damaging liver cells and their DNA. Acetaldehyde is also what makes alcohol a risk for multiple forms of cancer. With prolonged bouts of heavy drinking, your liver cannot properly recover and break down the alcohol and essentially becomes overworked (20).
There has been varying research into alcohol’s effects on cardiovascular health outcomes. Some studies have found that moderate wine consumption (1-4 drinks per week) lowered the risk of cardiovascular disease when compared to moderate drinking of beer or spirits and even compared to non drinkers (21). This is believed to be the result of a type of antioxidant called polyphenols found in red wine which may serve as a protective barrier for the lining of blood vessels for the heart. The association between improved heart health and moderate wine consumption has been particularly noted in Sardinia, Italy, a blue zone, with one of the world’s highest centenarian concentrations. These studies are all epidemiological though, so other lifestyle factors such as diet, exercise, and socioeconomic status may explain the association between wine consumption and improved cardiovascular health outcomes. Other studies have found that reducing general alcohol consumption results in lowered risk for mortality due to a heart health outcome. All studies, however, find that heavy drinking of any type of alcohol increases the risk for chronic heart conditions (22).
Associations between alcohol consumption and type-2 diabetes reflect similar results: “heavy consumption (>3 drinks/d) may be associated with up to a 43% increased incidence of diabetes”.
However, moderate to minimal alcohol consumption shows little to no association with diabetes and glucose control (23).
Alcohol is also a neurotoxin that disrupts communications between neurons that control memory, mood, motor skills and emotion, which leads to the short term feeling of being intoxicated and long term effect of declined fluid and crystallized intelligence (24). The long term neurodegenerative effects of alcohol also makes it a contributing factor towards chronic neurological illnesses such as Parkinson’s and Alzheimer’s (25). However, as alcohol consumption has dropped from record highs in the 1970s, rates of Alzheimer’s have steadily increased, which could demonstrate other lifestyle factors contribute to Alzheimer’s as well.
Smoking- both tobacco and marijuana- have been highly researched lifestyle factors pertaining to chronic illness. Tobacco, foremost, has been found to be an extreme risk factor for many negative cardiovascular health outcomes and chronic conditions. A 2023 systematic review of tobacco smoking’s effects on cardiovascular outcomes and overall health found: “Smoking cigarettes causes a chronic inflammatory state that aids in the development of atherogenic disease processes and raises levels of inflammatory biomarkers, which are known to be excellent indicators of cardiovascular events. Nearly every organ in the body suffers damage from smoking, which also increases the risk of illness and lowers smokers’ overall health”. The review also found that smoking tobacco will increase the risk for cardiovascular events even at low levels such as secondhand smoke (26). In addition to findings on smoking’s effects on cardiovascular health outcomes, researchers have found: “Among smokers, rates of cancer of the cervix, pancreas, bladder, kidney, stomach, and hematopoietic tissue are increased 50% to 200% over rates in nonsmokers” (27). Logically, since cancer and chronic cardiovascular conditions such as hypertension and coronary heart disease are leading causes of death in America, data from National Health Surveys have found that smoking increases all cause-mortality even at low levels (28).
Marijuana smoking has been found to have similar results on cardiovascular outcomes as tobacco smoking. A 2021 study found “frequent marijuana use was associated with 88% higher odds of myocardial infarction or coronary artery disease” (29). Prior tobacco smoking may seem like a confounding variable in the study, but the study was limited to patients who had never smoked tobacco. However, medicinal marijuana use, especially in patients with cancer undergoing chemotherapy, was found to have other positive effects that tobacco smoking lacked. A recent systematic review found that use of cannabis may help ease symptoms of chemo-induced nausea (30). It may be beneficial to use non-smoked forms of marijuana such as tinctures and edibles, to possibly ease the stress smoking puts on the lungs and cardiovascular system, while receiving the same benefits.
Cannabis has also been looked into as a risk factor and potential treatment for chronic mental health and neurodegenerative conditions. However, despite many anecdotal accounts of cannabis use easing anxiety and depression, overall scientific data is insufficient to make definitive conclusions, and more research must be conducted to confidently use cannabis as a preventative or symptomatic relieving measure for chronic mental conditions (31,32).
Arguably the most important lifestyle factor in determining overall health, longevity and avoidance of chronic disease is sleep. Multiple studies and systematic reviews have found that both shortened (6>= hours/day) and prolonged (8=< hours/day) resulted in an increased risk of all-cause mortality and cardiovascular disease (33,34). It appears that shortened sleep seems to be a more widespread risk factor for chronic health conditions and mortality. It is possible that prolonged sleep duration’s association with cardiovascular events and mortality is associated with its likelihood to accompany other poor lifestyle factors such as a poor diet, smoking and alcohol use. Shortened sleep periods only were found to be an independent risk factor for developing mental health conditions such as anxiety and depression (35).
Sleep duration is not the only factor that appears to affect chronic conditions and mortality. A recent study done in Ecuador found that sleep quality also indicated an increased risk for mortality in adults (36). In similar fashion, a 2021 meta analysis found sleep to be “causally related to the experience of mental health difficulties, and therefore that sleep represents a viable treatment target that can confer significant benefits to mental health” (37).
Overall health science research and the data presented demonstrates there is a clear relationship between the declining lifestyle choices of many Americans and declining health and increases in chronic health conditions. While genetic predispositions play a major role in chronic illness and for many these conditions cannot be prevented, diet, exercise, avoidance of drugs and alcohol, and sleep can play major preventative roles for many and can decrease the risk for mortality in those who have already developed chronic diseases. As obesity and chronic illness continue to persist and plague the American healthcare system, it is important to raise awareness on the importance of lifestyle medicine in solving this epidemic.
