The purpose of this report is to provide information about ways to mitigate and even reverse insulin resistance through lifestyle changes instead of pharmaceuticals. Methods include literature searches using PubMed and Google Scholar for articles related to the causes of insulin resistance and the effects of the ketogenic diet, intermittent fasting, and exercise on insulin resistance. Causes of insulin resistance include poor diet, obesity, especially visceral adiposity, and sedentary lifestyle. Over time insulin resistance can develop into nonalcoholic fatty liver disease (NAFLD). NAFLD can develop into nonalcoholic steatohepatitis (NASH) in the absence of lifestyle changes.
Eliminating refined carbohydrates in favor of high fiber and nutrient dense foods can reverse insulin resistance. Reducing saturated fats to include more monounsaturated and polyunsaturated fats have been shown to improve blood glucose levels and high density lipoprotein (HDL) to low density lipoprotein (LDL) blood profiles. The ketogenic diet is effective for weight loss and blood glucose control due to ketogenesis. The ketogenic diet produced long-term effects on glucose regulation that medications did not.
Intermittent fasting has been shown to improve health in several ways beyond weight loss. Intermittent fasting stimulates the metabolic switch from glucose and glycogen as a fuel source to the production of ketones as a fuel source. Ketones fuel fat loss, improve glucose metabolism, and decrease inflammation. Achieving weight loss through dieting alone resulted in improved insulin sensitivity, but also muscle loss. People who exercised to lose weight retained muscle and also reduced overall inflammation and liver fat, both mechanisms for insulin resistance. Exercise combined with caloric restriction produced significantly more beneficial physiological changes and hormonal responses than did exercise or diet alone. Intermittent fasting and exercise both produce autophagy. Autophagy enables DNA repair, mitochondrial biogenesis, and reduction of loose skin that can occur during weight loss. It is recommended that those with insulin resistance engage in permanent lifestyle changes to reduce or eliminate insulin resistance and chronic diseases associated with insulin resistance in order to promote health.
Insulin resistance is the most prevalent hormone imbalance in America. More than 50 percent of Americans suffer from insulin resistance and most are unaware of it [1]. Insulin resistance is a reduction of glucose transport and absorption by cells resulting in a decrease in energy in cells, which triggers appetite to replenish energy in cells resulting in overeating and fat [1]. Being overweight or obese means being at two times higher risk of developing Type 2 Diabetes. Fat metabolism disorders are predominant in patients with Type 2 Diabetes leading to increased free fatty acids circulating in the blood, which increases insulin resistance and factors for cardiovascular diseases. Additionally, there is a correlation between visceral fat (fat in and around organs and muscles in the abdominal cavity) and nonalcoholic fatty liver disease (NAFLD) [2]. Visceral fat increases the odds of insulin resistance by 80 percent [2]. Visceral fat results in a condition known as lipotoxicity because it releases inflammatory cytokines, which impair insulin sensitivity. Therefore, visceral fat is associated with insulin resistance because it secretes cytokines that impair insulin sensitivity in liver and muscle tissue [2]. This report presents information on the effects of diet, intermittent fasting and exercise on insulin resistance. The purpose is to provide information about ways to mitigate and even reverse insulin resistance through lifestyle changes instead of pharmaceuticals.
Nonalcoholic fatty liver disease (NAFLD) is attributed to obesity, insulin resistance, and Type 2 Diabetes. It eventually leads to chronic liver disease in the absence of dietary changes [3]. NAFLD is prevalent in about 30 percent of adults and children in the United States [3]. People with Type 2 Diabetes have a five times higher risk for developing NAFLD. NAFLD is generally asymptomatic until advanced [3]. Permanent changes in diet can reverse NAFLD. Dietary causes of insulin resistance and NAFLD include heavy consumption of refined carbohydrates in highly processed foods. In addition to sugar and refined carbohydrate diets, a high saturated fatty acid (SFA) diet greater than 10 percent of total caloric intake stimulated insulin resistance, elevated low density lipoprotein (LDL) cholesterol, and triglyceride levels that contributed to NAFLD [4]. Conversely, a diet between 7 and 10 percent SFA produced the opposite effects. However, ingestion of monounsaturated fatty acids found in organic olive oil, soy, sunflower, nuts and avocado induces healthy blood glucose levels and generates high density lipoprotein (HDL) cholesterol while lowering LDL cholesterol and triglycerides [4]. Polyunsaturated fatty acids found in fish, green leafy vegetables, and flaxseeds reduce visceral fat levels, decrease insulin resistance, and improve NAFLD [4].
The ketogenic diet has been shown to induce fat loss and reduce or illuminate insulin resistance and Type 2 Diabetes [5][14]. The ketogenic diet involves the incomplete oxidation of fatty acids in the liver. This results in the accumulation of ketones in the body. Ketones alter the body’s fuel source from glucose and glycogen to fat [5][14]. Fat metabolism increases thereby decreasing fat stores in the body including visceral fat [5][14]. The ketogenic diet combined with intermittent fasting is effective for weight loss and blood glucose control. Intermittent fasting can reverse insulin resistance, Type 2 Diabetes and NAFLD. Intermittent fasting has been shown to reduce inflammation and some chronic diseases [18]. Intermittent fasting done to induce autophagy removes damaged cells and improves tissue plasticity. Autophagy literally means "self-eating" [18]. Autophagy is the process the enables the body to recycle or destroy damaged cells in order to promote new collagen production and create new cells [18]. Reducing body fat regardless of method improved insulin uptake significantly. However, the method chosen for weight loss induces different physiological changes and hormonal responses [18].
A literature search was performed for articles related to the effects of the ketogenic diet, intermittent fasting and exercise on insulin resistance and NAFLD. PubMed and Google Scholar were used to search for published articles including case reports, clinical trials and randomized controlled trials between the years of 2010 and 2023. Sports medicine articles and physician blogs were also included. Inclusion criteria included full text published articles in English free to the public. Exclusion criteria included duplicates, abstracts, non-English articles, articles published before 2010, and unrelated content articles. Keywords used included "insulin resistance," "obesity," "Diabetes," "NAFLD," "ketogenic diet," "intermittent fasting," "cytokines" "aerobic exercise," "resistance training," "ketones," "autophagy" and “tissue plasticity.” Articles that met the criteria were further reviewed. A total of 18 reports and articles were included in the reference list.
Research was separated into five topics most relevant to insulin resistance:
1. Causes of Insulin Resistance: Causes of insulin resistance include poor diet, obesity, especially visceral fat, and sedentary lifestyle. Poor diet includes heavy consumption of soft drinks, high fructose corn syrup, and refined carbohydrates in highly processed foods that lead to obesity, insulin resistance and Type 2 Diabetes. A diet high in saturated fat leads to metabolically active visceral fat and general obesity. Lack of exercise to burn excess calories and build lean muscle mass increases body fat and decreases insulin uptake.
2. Insulin Resistance and Nonalcoholic Fatty Liver Disease: Insulin resistance can develop into nonalcoholic fatty liver disease (NAFLD) while NAFLD can develop into nonalcoholic steatohepatitis (NASH). Insulin resistance, Type 2 Diabetes and obesity are attributed to NAFLD. NAFLD can lead to NASH, a much more aggressive form of liver disease. NAFLD can be reversed with lifestyle changes. However, NASH causes permanent liver damage. Both NAFLD and NASH are asymptomatic.
3. Effects of Diet on Insulin Resistance: Eliminating sugar and refined flour products in favor of high fiber, nutrient dense foods can reverse insulin resistance. Exchanging high saturated fats for monounsaturated and polyunsaturated fats will improve blood glucose levels and improve HDL to LDL blood profiles. The ketogenic diet is effective for weight loss and blood glucose control due to ketogenesis when the body switches from glucose and glycogen as a fuel source to fatty acids derived from fat stores and is converted into ketones by the liver. Ketogenesis reduces body fat, improves blood glucose and decreases insulin production.
4. Effects of Intermittent Fasting on Insulin Sensitivity: Intermittent fasting stimulates the metabolic switch from glucose and glycogen as a fuel source to the production of ketones as a fuel source. This metabolic switch occurs within about 8 to 12 hours during a fast. Ketones fuel fat loss, improve glucose metabolism, decrease inflammation, and preserve lean muscle mass even while fasting. Intermittent fasting can reverse insulin resistance, Type 2 Diabetes and NAFLD. Intermittent fasting done for the purpose of autophagy enables DNA repair and mitochondrial biogenesis thought to diminish neurological and autoimmune diseases. Autophagy has cosmetic benefits as well such as decreasing or eliminating saggy skin during weight loss.
5. Effects of Exercise on Insulin Sensitivity: Weight loss through dieting alone resulted in improved insulin sensitivity, but also resulted in muscle loss. Exercise combined with caloric restriction retained muscle and produced significantly more beneficial physiological changes and hormonal responses than did exercise or diet alone. Retaining muscle while losing fat improves glucose uptake considerably because lean muscle mass consumes glucose as a fuel source. People who exercised to lose weight also reduced overall inflammation and liver fat, both mechanisms for insulin resistance.
Insulin is a hormone produced by the pancreas to increase glycogen and glucose uptake by the body’s cells in order to convert glycogen and glucose into energy. Insulin resistance is a condition whereby the body’s cells do not respond to insulin as they should. When too much insulin is circulated in the bloodstream over prolonged periods of time it affects metabolism [16]. Cells stop responding to insulin. When cells stop responding to insulin they are not being fed [16]. Cells then signal the brain telling it hunger persists resulting in overeating coupled with an inflammation response [16]. Over time the inflammation response causes chronic diseases including Type 2 Diabetes and coronary artery disease [16]. Symptoms of insulin resistance include obese waist, skin tags, blurred vision, fatigue, frequent urination, and excessive thirst [6].
Most scientists believe that being overweight and sedentary are the two main causes of insulin resistance. Insulin resistance can eventually lead to Type 2 Diabetes, which can lead to nonalcoholic fatty liver disease (NAFLD) if lifestyle changes are not made. A relationship between visceral obesity, insulin resistance and Type 2 diabetes exists [2]. Visceral obesity results in insulin resistance whereas subcutaneous fat does not. Unlike visceral fat, subcutaneous fat is not indicative of insulin resistance [2]. That may be due to visceral fat secreting inflammatory hormones. Visceral adipose tissue (fat) in particular is dangerous to overall health because it secretes toxins that exacerbate insulin resistance. The mechanism is the release of both inflammatory and anti-inflammatory hormones in the form of leptin and adiponectin, respectively [7]. Leptin helps to regulate body weight through signaling the brain to suppress appetite [7]. Adiponectin increases lean muscle mass and fat oxidation while increasing glucose uptake [7]. Visceral fat is the most dangerous type of fat and is associated with heart and liver diseases. The more visceral fat a person has the less adiponectin a person has [7].
Nonalcoholic fatty liver disease (NAFLD) is attributed to obesity, insulin resistance and Type 2 Diabetes. NAFLD eventually leads to chronic liver disease in the absence of dietary changes. NAFLD is prevalent in about 30 percent of adults and children in the United States [3]. Of those suffering from Type 2 Diabetes, 60-80 percent develop NAFLD [2]. People with Type 2 Diabetes have a five times higher risk for developing NAFLD. Of those suffering from NAFLD, up to one-third develop nonalcoholic steatohepatitis (NASH), a much more aggressive form of liver disease that can lead to cirrhosis, cancer, and liver failure [2]. These chronic liver diseases are attributed to high sugar and refined carbohydrate diets [9]. Whereas NAFLD is asymptomatic and can only be detected through ultrasound, NASH can only be detected by a liver biopsy [2]. Risk factors for NASH include high blood pressure, Type 2 diabetes, and obesity [2]. Symptoms of NAFLD may include a potbelly and ascites, but is generally asymptomatic until advanced.
Heavy consumption of soft drinks, high fructose corn syrup, and refined carbohydrates in highly processed foods has increased obesity worldwide, but particularly in the United States [2]. Additionally, aspartame in diet soft drinks is a peptide ester that causes weight gain and increases risk for Type 2 Diabetes [2]. One study conducted on adult men showed that high fructose soft drinks increase insulin resistance, stimulate NAFLD, and raise blood triglycerides [2]. Consuming more than one high fructose soft drink per day greatly increases metabolic syndrome development. This risk does not occur in those who do not consume any high fructose soft drinks. High fructose corn syrup comes from genetically modified (GMO) corn to increase sweetness [2].
In addition to sugar and refined carbohydrate diets, a high saturated fatty acid (SFA) diet greater than 10 percent of total caloric intake stimulated insulin resistance, high low-density lipoprotein (LDL) cholesterol, and triglyceride levels that contributed to NAFLD [4]. Conversely, a diet between 7 and 10 percent SFA produced the opposite effects [4]. But a diet lower than 7 percent SFA was as detrimental to the patient as a diet higher than 10 percent [4]. Therefore, total daily SFA should be greater than 7 percent but less than 10 percent of total calories [4]. Trans fats from hydrogenated vegetable oils produce inflammation in the body and disturb lipid profiles no matter the amount ingested and should be avoided completely [4]. Trans fats are genetically engineered (GMOs) fats created to increase shelf life of baked goods, margarine, and other food products [4].
Monounsaturated fatty acids in the form of organic olive oil, soy, sunflower, nuts and avocado are Omega 3 fatty acids and very good for human lipid profiles [4]. Ingestion of monounsaturated fatty acids induces healthy blood glucose levels and blood pressure and generates high-density lipoprotein (HDL) cholesterol while lowering low-density lipoprotein (LDL) cholesterol and triglycerides [4]. Unrefined organic extra virgin olive oil (first cold press) in particular prevents metabolic syndrome responsible for insulin resistance and has many bioactive constituents and anti-oxidative properties [4].
Polyunsaturated fatty acids found in fish, green leafy vegetables, and flaxseeds reduce visceral fat levels, decrease insulin resistance, and improve NAFLD [4]. Fish oil high in EPA and DHA had the greatest positive effect on insulin resistance in human and animal studies [4]. In fact, EPA and DHA deficiency can develop into NAFLD in both humans and animals. Omega 6 fatty acids found in eggs, animal fat, and cereals contributed to the development of NASH in patients, but when substituted for Omega 3 fatty acids, improved insulin sensitivity and LDL cholesterol substantially [4]. Of these two types of fats, the healthiest ratio of Omega 3 to Omega 6 is 1:1 to 1:4. Monounsaturated fats are healthier for human liver, cholesterol, and blood sugar levels than polyunsaturated fats [4].
High protein and low carb intake decrease NAFLD [4]. Chronic protein deficiency and malnutrition can lead to the development of NASH. High protein intake that displaces high carb intake inhibits lipogenesis in the liver and decreases liver steatosis (fatty liver) involved in NASH. High protein intake also decreases insulin output. Whereas a high fat diet like that in the ketogenic diet is detrimental to patients suffering from NASH, a high protein diet is beneficial. However, keto has been shown in studies to decrease NAFLD that has not progressed to NASH [8]. In addition to decreasing liver steatosis involved in NASH, a diet consisting of 40 percent protein vs. a diet consisting of 15 percent protein reduces visceral fat and reduces cardiovascular disease [8]. However, high protein intake is bad for the kidneys and prolonged ingestion can result in kidney failure. Moderate protein intake of 25 percent of total daily calories is best for overall health and still results in the same reduction of visceral fat as the high protein diet [4]. There were no side effects involved in studies with moderate protein intake [4].
Some studies have shown that complex carbohydrates with high fiber intake of 40-50 percent of daily calories is beneficial for NAFLD patients [4]. Other studies show that the ketogenic diet greatly improves or reverses NAFLD. Regardless of the method, lifestyle changes are vital for managing insulin resistance and NAFLD. Since NAFLD is asymptomatic, many people go undiagnosed until it develops into late stage diseases like NASH with cirrhosis, cancer, and liver failure. People who are obese and who have Type 2 Diabetes should have a liver ultrasound performed to detect fatty liver disease that may have developed into NAFLD. If fatty liver disease appears to be advanced, a liver biopsy for NASH and fibrosis should be performed to enable immediate corrective action. The minor form of liver disease, NAFLD, can be prevented or reversed with proper diet including the ketogenic diet. Reversing NAFLD requires permanent changes in diet and takes between 9-12 months [9].
The kegotenic diet was originally developed to control seizures in epileptic patients in the 1920s and 1930s [5]. It is believed that the ketones produced by the ketogenic diet do not cause convulsions when crossing the blood-brain barrier [5]. The ketogenic diet transitioned from being used to control seizures in epileptic patients to being used to induce weight loss in obese patients due to its low carbohydrate intake [5]. In the ketogenic diet, ketones are released from the breakdown of body fat which is used as fuel instead of glucose. This ketotic state alters metabolism and stabilizes neurons involved in epilepsy [5]. The ketogenic diet is high in fat, low in carbs, and moderate in protein. Carb intake is between 20 to 50 grams per day from non-starchy vegetables like kale, broccoli, green salads, etc. Protein is high enough to maintain muscle, but low enough to maintain ketosis because the amino acids alanine and glutamine can be converted into glucose and end ketosis. The brain is usually dependent on glucose and cannot use fatty acids as fuel directly but ketones converted from fatty acids by the liver can cross the blood-brain barrier and provide fuel for the brain. The ketogenic diet has been observed inducing gene expression in the brain which might account for the suppression of seizures in epileptic patients [5].
Because fat is higher in calories than carbohydrates, most people believe that a high fat diet leads to obesity and coronary artery disease. This study showed that a high fat ketogenic diet reduced fat stores and the risk of heart disease in obese patients [5]. Since incomplete oxidation of fatty acids in the liver results in the accumulation of ketones in the body, ketosis occurs that alters the body’s fuel source from carbohydrates to fat [5]. Therefore, fat metabolism increases thereby decreasing fat stores in the body including visceral fat.
Diet is the simplest and most cost effective way to control weight in obese people [14]. Using medication to control blood sugar provides a temporary effect on blood glucose levels whereas dietary intervention provides a long-term effect on blood glucose levels [14]. The ketogenic diet in particular induces a state of fasting, causes a metabolic switch from glycogen to ketones, and is known to effectively promote weight loss and insulin uptake [14]. The ketogenic diet involves consuming 85% to 90% calories from fat, 10% from protein, and 5% from carbs [5]. However, protein intake should be increased for individuals performing weightlifting to build and maintain muscle. Also, some people choose to increase carbs to 25-50 grams per day to increase fiber and phytonutrient intakes. The keto diet produced long-term effects on glucose regulation that medications did not. According to Dashti, Mathew and Hussein (et. al.,) in one study, "heart and vascular complications reduced by 14% and 37%, respectively" [5]. This meta-analysis concentrated on weight reduction in obese diabetic patients utilizing the ketogenic diet [5]. It resulted in fat loss, especially visceral fat, reduced blood pressure, and improved insulin resistance and fat metabolism, which also decreased fatty liver [5]. This meta-analysis involved 13 studies on the ketogenic diet and its effects [5]. All were effective at reducing body weight, controlling blood glucose and insulin levels, and improved fat metabolism [5]. Those who practice the ketogenic diet lose more weight and keep it off compared to those on low fat diets. They also experience less hunger and have higher metabolisms than low fat dieters.
While a complete transition from glucose to ketones as a fuel source takes about a week, after a few days of following the ketogenic diet, the body changes its energy metabolism and begins to use fat instead of glucose as an energy source thereby reducing insulin production [5]. However, there are side effects when beginning the ketogenic diet that include fatigue, headache, nausea and vomiting known as the "keto flu" [5]. All these side effects were mild and subsided in time (after two weeks) [5]. Hunger was also experienced in the beginning, but dissipated significantly over time [5]. Other negative side effects of the ketogenic diet included elevated LDL blood cholesterol and liver enzymes, especially in those with NASH [5]. Patients with NASH should not participate in the keto diet [5].
Intermittent fasting has been shown to improve health in several ways beyond just losing weight. In ancient societies, fasting was used for healing diseases and improving cognitive abilities [7]. Intermittent fasting can reverse insulin resistance in Type 2 Diabetes patients, improve neurological disorders like Alzheimer’s and Parkinson’s Disease, reduce inflammation that causes atherosclerosis and rheumatoid arthritis, and finally, it can reduce cancer cells by inhibiting their ability to function [7]. Intermittent fasting improves glucose tolerance and reduces free radicals and inflammation [7]. It also removes damaged cells and improves tissue plasticity once autophagy begins.
During fasting, the body’s glucose supply is quickly consumed. Thereafter, the main energy source is ketones created by the liver from fatty acids. This metabolic switch occurs within about 8 to 12 hours during a fast [7]. According to de Cabo and Mattson, ketones are not just the body’s energy source [10]. Ketones "regulate the expression and activity of many proteins and molecules that are known to influence health and aging" [10]. The most popular methods of intermittent fasting are alternate day fasting, 5:2 intermittent fasting, and daily time restricted feeding [7]. Alternate day fasting is fasting for 24 hours every other day in order to generate the metabolic switch from glycogen to ketones as a fuel source. The 5:2 method is fasting two days a week in order to promote autophagy and the metabolic switch [7]. Time restricted feeding occurs when food is consumed within a four, six, eight, or twelve hour window within a 24-hour period and fasting occurs for the rest of the day. For example, consuming only breakfast and lunch within a six hour window and fasting the rest of the day is a popular method of intermittent fasting [7]. Intermittent fasting can be performed for 48 hours or longer. Nevertheless, ketosis plateaus after 4 days with diminishing returns during fasting alone. However, ketosis can be maintained with high fat diets such as the ketogenic diet [13]. Even so, some people find that intermittent fasting, especially restricted feeding, is easier to maintain and more practical than the ketogenic diet or caloric restriction diets [7].
Intermittent fasting and the production of ketones stimulate fat loss and improve glucose metabolism [7]. However, not all types of fasting confer the same results. In one study, participants who engaged in the 5:2 intermittent fasting regimen or the reduced caloric intake regimen had differing results [10]. While both groups lost the same amount of weight, the 5:2 group reduced more visceral fat and experienced better insulin uptake [10]. Further, while intermittent fasting and caloric restriction both induce about the same amount of weight loss, only intermittent fasting for 24 hours three times a week "reversed insulin resistance" in patients suffering from Type 2 Diabetes and prediabetes [10].
Ketones and autophagy have also been shown to improve neurodegenerative disorders like Alzheimer’s and Parkinson’s Disease [10] [18]. Both intermittent fasting and caloric restriction regimens have been shown to improve cognitive function in aging adults [10] [18]. Intermittent fasting used to promote autophagy improves tissue plasticity. Autophagy typically occurs after 24 hours of fasting with benefits diminishing after 32 hours of fasting [10] [18]. During autophagy the body consumes and recycles damaged cells to promote new cell growth and collagen production. Autophagy enables DNA repair and mitochondrial biogenesis [10]. One study found that the cells responsible for producing collagen known as fibroblasts become "clogged" with cellular waste over time and are unable to function properly unless autophagy occurs to clear out cellular waste [18]. Autophagy reduces loose skin that occurs during weight loss for overweight and obese people [18]. Combining exercise with intermittent fasting induces autophagy even more, particularly strength training and intermittent fasting [18]. However, autophagy cannot occur in people who regularly consume three meals per day plus snacks or who live sedentary lives.
Reducing body fat by 10 percent regardless of method improved insulin uptake significantly [11]. Weight loss due to dieting alone resulted in improved insulin sensitivity, but also in muscle loss. Retaining muscle while losing fat is optimal because glucose uptake is considerably increased [11]. Conversely, people who exercised to lose weight reduced overall inflammation and liver fat, both mechanisms for insulin resistance [11]. Aerobic exercise is the most common treatment method for improving insulin sensitivity in people because it induces weight loss, which includes visceral fat. Including resistance training of 9 exercises of 3 to 4 sets of 8 to 10 repetitions three times per week enhances insulin sensitivity beyond aerobic exercise and increases lean muscle mass, which escalates resting metabolic rate throughout the day [11]. Using caloric restriction to induce fat loss compared to using exercise to induce fat loss produced similar results in insulin uptake response. But exercise combined with caloric restriction "stimulates mitochondrial oxidative capacity and impacts endogenous glucose production by significantly suppressing unnecessary gluconeogenesis" according to Keshel and Coker [11]. Consequently, the method chosen for weight loss induces different physiological changes and hormonal responses.
High intensity interval training (HIIT) may be more effective at reducing subcutaneous and abdominal fat than any other exercise [12][16]. It also significantly lowers insulin resistance and increases fat oxidation and glucose uptake. However, cortisol does increase during HIIT sessions and increased cortisol worsens insulin resistance [12][16]. Cortisol dominant people should not begin an exercise regimen with HIIT. Cortisol dominant people should begin with low intensity exercise like walking, Pilates, weight machines, swimming, yoga, etc. [12]. Once stress levels decrease, cortisol dominant people can incorporate HIIT once or twice a week followed by more low intensity exercise to ease into it [12][16]. HIIT has resulted in improved insulin uptake of between 23 percent and 58 percent [12].
Dieting alone to lose weight can cause a 35 percent reduction of lean muscle mass for people at normal weight and a 20-30 percent reduction of lean muscle mass for overweight and obese people [15]. Diet combined with resistance training prevents loss of lean muscle mass [15]. Consuming a whey protein supplement right after resistance training also prevented loss of lean muscle mass while dieting [15]. However, too much protein induces insulin resistance because amino acids alanine and glutamine can be converted into glucose by the liver. Therefore, diet, including a moderate amount of protein, combined with resistance training and cardiovascular exercise induces the greatest amount of weight loss and insulin uptake while preserving muscle thereby improving overall physical function and health [15].
According to Yuan, Wang, and Gao, (et. al.), over 300 million people worldwide have diabetes and that number will increase by 55 percent by 2035 [14]. Over time, too much insulin increases fat stores and causes inflammation that lead to chronic diseases including atherosclerosis, coronary artery disease, Type 2 Diabetes and NAFLD [17]. The number of people suffering from these types of chronic diseases could be reduced if people would make changes to diet and physical activity. The ketogenic diet and intermittent fasting combined with exercise are effective methods for weight reduction and insulin regulation. Autophagy induced through fasting and exercise reduces inflammation, improves cognition and increases lifespan by enabling the body to recycle or destroy damaged cells in order to promote new cell production [13][18]. Ancient civilizations fasted to cure disease and improve cognition whereas Western Civilization relies on pharmaceuticals to mitigate symptoms of chronic diseases that could be cured through proper nutrition and exercise. It is recommended that those with insulin resistance engage in permanent lifestyle changes to reduce or eliminate insulin resistance and chronic diseases associated with insulin resistance in order to promote health and longevity.
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