Introduction
Obesity has become a serious health concern issues because of it is a health risk factor that affects “cardiovascular and metabolic disorders such as hypertension, type 2 diabetes, dyslipidemia, atherosclerosis and certain types of cancers” (Paoli, 2014). People get obesity when they acquire a given body mass index. People with 25-29.9 BMI are considered overweight, whereas others with 30 or more BMI are considered obese. Obesity is related to several chronic conditions such as heart diseases, diabetes, cancer and stroke among others.
There are several recommendations and approaches on weight loss, but these strategies have often failed. Cases of obesity have increased since 1980s globally. In addition, there are many deaths related to obesity. For many healthcare providers, they have to deal with serious cases of overweight and obesity with difficulties because many recommended solutions seem not to work for patients. Some of these recommendations for obesity treatment include diets, exercise, medication and bariatric surgery. The main consensus regarding obesity management has been reducing energy intake and enhancing physical activities.
Diet has remained the most controversial means of obesity and overweight management because various strategies have been adopted. There is however little empirical results to support outcomes of such interventions.
This literature review explores carbohydrate count by focusing on ketogenic diets (KDs) because of the increased interest in the topic in the recent years as an intervention for obesity and overweight management.
Significance of the topic
Many studies have referred to ketogenic diet (KD) as a low carbohydrate, high fat diet which decreases blood glucose and elevates blood ketones by altering metabolism (Abdelwahab et al., 2012; Poff, Ari, Seyfried, & D’Agostino, 2013). Since diets have gained popularity in managing obesity and overweight, the main challenge remains the most suitable nutritional strategy.
As a result, the main dietary approach has been high-levels of carbohydrates and low fat content, but according to some studies these low fat diets yield only modest weight losses and suffer from low long-term compliance issues” (Paoli, 2014). At the same time, some studies have highlighted that high carbohydrate and low fat diets are potential source of problems because many obese individuals tend to prefer foods with high concentration of fats. People with obesity also consume high amount of processed foods with high sugar contents.
This could facilitate consumption of simple carbohydrate and sugar instead of complex carbohydrates. In this regard, consumption of simple sugar and carbohydrates can facilitate overweight and obesity. Therefore, consequences of these diets have brought about debatable concerns in public health, which have enhanced interests in “Very Low Carbohydrate Ketogenic Diets (VLCKDs) or simply ketogenic diets (KDs)” (Paoli, 2014).
Ketogenic diet is useful for treatment and management of various conditions and diseases in both human and animals (Paoli, 2014; Abdelwahab et al., 2012; Poff et al., 2013). In addition to these interventions, ketogenic diet is known for its role in weight loss and obesity management. Some studies have confirmed that ketogenic diets have shown effectiveness in obesity, cardiovascular risk factors and hyperlipidemia management in short-term to medium-term interventions (Paoli et al., 2012).
At the same time, physicians have also raised some concerns about ketogenic diets. Many challenges about the use of ketogenic diets could be related to knowledge gap because the study is relatively new, particularly the physiological processes involved. Ketogenic diets are responsible for metabolic situations referred to as “physiological ketosis, which highlights its difference from pathological diabetic ketosis” (Paoli, 2014).
During the past several decades, obesity rates for all population groups—irrespective of “age, sex, race, ethnicity, socioeconomic status, education level, or geographic regions—have increased markedly” (Centers for Disease Control and Prevention, 2011). Obesity has become a national health problem.
Today, it is linked to other chronic diseases, such as hypertension, coronary heart diseases, diabetes, stroke, osteoarthritis, and some types of cancers. Although several factors could be responsible for obesity in the world, poor diets and a lack of physical activities, seem to be the major contributors to obesity.
Self-management interventions, however, have not been highly successful because of chronic conditions among the target populations. Nevertheless, they provide the most basic approaches that nurses may adopt and assist obese and overweight individuals to modify their behaviours and lifestyles. Such interventions have various options that match different needs, interests, functional limitations and lifestyles. Consequently, interventions aim to encourage older adults to pursue various activities and enhance their physical well-being. Interventions on physical activities point out barriers that affect physical activities among seniors.
In addition, they note that care providers should address factors related to home and community, healthcare policy and advocacy programmes and other related issues to overcome challenges to physical activities. The main approaches in these interventions have been the following.
First, such interventions disseminate information about advantages of physical exercise for obese and overweight people. Such people can gain access to such information through professional journals, specialised magazines, meetings or from health professionals. Second, interventions aim to identify and provide specific diets and physical activities that meet various needs of people with obesity and other chronic conditions, including arthritis.
They help patients to pursue activities that will improve their physical well-being. Finally, they also offer resources that describe physical exercise opportunities for people with obesity and other chronic conditions. This allows nurses and other care providers to offer appropriate support, referrals and recommendations.
It is imperative to note that older adults present unique challenges when focusing on behaviour changes, diets, lifestyles and physical activities. Generally, increase in and several cases of chronic conditions in older adults affect diets and the level of physical activities and exercise engagement. These factors results in difficulties in losing weight among seniors. In addition, it is necessary to focus on depression and related causes among older adults. Obese people, therefore, require support of other people to take part in these activities to encourage them.
Ketosis
Insulin is responsible for activating enzymes with stored energy obtained from carbohydrates. When there is a shortage of dietary carbohydrates, there is a reduced level of insulin, which leads to a low-level of fat and lipogenesis concentration. Consumption of reduced carbohydrate will fall drastically within few days. At the same time, glucose deposits may fail to compensate for normal fat oxidation through the available oxaloacetate and glucose supply to the nervous systems.
The central nervous system cannot rely on fat as its source of energy because it depends on glucose to provide energy. Therefore, after more than three days without carbohydrate, the central nervous system will search for other sources of energy, which mainly come from excessive generation of acetyl coenzyme A (CoA). If fasting continues, then high fat or low carbohydrates will produce excess amount of ketone bodies through a ketogenesis process. This process takes place in the mitochondrial matrix within the liver.
It is imperative to recognize that ketosis is a physiological process, which takes place in the presence of ketogenic diets.
Ketogenic Diet for Obesity and Weight Loss Management
Some of the major issues that many studies have explored in ketogenic studies include their effectiveness, human safety and outcomes on weight management. There are several empirical studies to support the effectiveness and the use of ketogenic diets in weight loss. However, the process of weight loss through these diets largely remains debatable. Originally, a study indicated that weight loss resulted from losing energy by elimination of ketone elements (Paoli, 2014).
Today, however, new studies have shown that there are different ways of weight loss through ketogenic diets. First, the use of body energy from protein generated from ketogenic diet is a complex, demanding process that leads to energy wastage and therefore facilitates energy loss (Westerterp-Plantenga, Nieuwenhuizen, Tome, Soenen, & Westerterp, 2009). This process involves gluconeogenesis, which is an energy demanding process because of protein and endogenous (Paoli, 2014).
In this case, still there is no empirical evidence to support this claim. At the same time, a recent study established that “one of the main weight loss mechanisms of KD might be attributed to an improvement in resting nutrient oxidation and interestingly this effect was long lasting, at least for up to 20 days following cessation of the ketogenic” (Paoli et al., 2012). Second, some studies have linked ketogenic diets to reduction in appetite among users because of “higher satiety effect of proteins” (Westerterp-Plantenga et al., 2009) or to some effects on appetite control hormones (Sumithran et al., 2013).
Third, some studies have suggested that weight loss could result from possible direct appetite suppression by ketone bodies, particularly by the BHB (energy/satiety signal and central satiety signal). Finally, fat loss outcomes could also originate from long-term improvement in fat oxidation (Paoli et al., 2012). This could result into lower rates of RR (respiratory ratio) and affect the diet.
Diets require strict regulation of food intakes. In this case, a negative energy balance plays a significant role in achieving weight loss. Therefore, in most cases, the main recommendation for any weight loss and obesity management program involves a reduction in amount of energy intake (Seagle, Strain, Makris, & Reeves, 2009).
Dietary reduction may depend on several factors such as energy, macronutrients elements, energy constituents or a combination of all these factors alongside other issues like meal frequencies, consistency, timing, guidance, food portions and strategies. In this case, understanding human eating behaviours is mandatory. Eating behaviours connect internal processes of human to their external environments. A reduced food intake could result from negative impacts on homoeostatic system.
This could be a disturbance or unsuitable signals (Seagle et al., 2009). In this sense, ketogenic diets have abilities to affect homoeostatic system negatively and suppress food intake (Sumithran et al., 2013).
Ketogenic Diets Beneficial Effects in Obesity
Some researchers have noted that ketogenic diets have other benefits beyond obesity and weight loss management (Davidson et al., 2013; Paoli, Rubini, Volek, & Grimaldi, 2013). For instance, other researchers have noted that ketones may offer cognitive protection against impairment due to obesity and weight gain (Davidson et al., 2013). In addition, others have suggested that ketogenic diets could improve the moods of obese and overweight people (Brinkworth, Noakes, Clifton, & Buckley, 2009).
This study noted that effects of ketogenic diets on physical activities and exercise tolerance in obese and overweight individuals were largely unexplored. It is imperative to note that ketogenic diets may cause lethargy among obese and overweight people, but such effects improve fast and increased mood is noted.
There are cases of insulin resistance obesity in obese patients. This, however, lacks adequate evidence. Nevertheless, some studies have noted resistance to insulin in some obese subjects (Paoli, 2014). The main feature in insulin resistance results from the inability of muscle cells to facilitate circulation of sugar in the body (Paoli et al., 2013).
In addition, there is also a reduction in hepatic glucose release. This suggests that people with insulin challenges have serious problems related to metabolism of dietary carbohydrate and will transfer a substantial amount of carbohydrate to the liver where it will be changed to fat. This is contrary to oxidization that results in energy production for the muscles. In this regard, one can conclude that effects of very low carbohydrate diets in obese people are numerous and not only weight loss as such.
Instead, ketogenic diets offer enhanced “glycaemic control, haemoglobin A1c, and lipid markers, as well as reduced use or withdrawal of insulin and other medications in many cases” (Paoli, 2014). These conditions lead to substantial weight loss. In addition, obese people with insulin resistance cases also realised improved metabolic activities in isocaloric studies relative to low fat diets.
Another significant impact of ketogenic diets is related to longevity. In this case, studies in animals have suggested such outcomes (Poff et al., 2013). For instance, ketogenic diets increased longevity in mice by blocking Mtor/AKT pathway. At the same time, a ketogenic diet also reduces serum ratio, which results in positive outcomes in metabolic conditions and risks of cancer.
Long-term Outcomes of Ketogenic Diets
The major purpose of ketogenic diet is to fast enhance a significantly large weight loss while offering substantial nutrition and maintaining a lean body weight as much as necessary. In this process, it is necessary to offer medical monitoring because of the fast weight loss process. Moreover, medically, it would be risky for individuals with less than 30 BMI to engage in very low energy diet activities.
While studies have suggested that strict adherence to very low energy diets resulted in a significant weight loss, maintenance of such weight loss on a long-term basis has become a critical challenge for many obese and overweight individuals under such diets (Brinkworth et al., 2009; Paoli, 2014; Seagle et al., 2009; Sumithran et al., 2013).
Seagle et al. (2009) noted that in 1998, the NHLBI expert panels warn against the use of very low energy diets because there was a lack of any significant long-term benefits relative to low energy diets. Moreover, greater weight regain was associated with very low energy diets (Seagle et al., 2009). At the same time, many studies have assessed the long-term of effects of very low energy diets on weight loss and obesity management. Many of these studies, however, have been case series with no significant comparisons and outcomes.
In most cases, overweight and obese individuals focus on reducing their body weight by reducing carbohydrate counts in their diets as a weight loss method. This results in the depletion of carbohydrate in the body because of low levels of carbohydrate consumption. The resultant dieresis causes a rapid weight loss. The body reacts to very low carbohydrate diets by releasing ketones to sustain fuel utilisation in the brain, which may in turn help with “diet adherence by decreasing hunger” (Seagle et al., 2009; Davidson et al., 2013).
Today, the use of very low energy diets has been preferred to bariatric surgery because of risks associated with surgery, particularly in individuals with severe cases of obesity. At the same time, some researchers have established that the use of very low energy diets for more than two weeks could result in a smaller liver, but further studies are necessary to assess such outcomes (Seagle et al., 2009).
Safety of Ketogenic Diets for Obese and Overweight Subjects
Many researchers have raised concerns regarding ketogenic diets, particularly with the issue of blood lipids (Paoli, 2014). In this regard, low-levels of carbohydrate with high concentrations of fat and protein diets have significantly unhealthy effects and could result in the rise of cholesterol. This issue is critical, specifically among obese individuals. Nevertheless, there are many studies, which highlight health benefits of KDs on cardiovascular conditions and related risk factors. The outcomes are mainly associated with low reduction on cholesterol and blood triglycerides.
Another safety issue involves possible negative consequences on renal functions. Usually, high concentration of nitrogen excretion in protein metabolism process may result in an “increased level of glomerular pressure and hyper-filtration” (Paoli, 2014). People with normal renal functions but on higher protein diets have developed morphological adaptation and therefore, there is no negative impact on their renal excretion. On the other hand, it is imperative to consider “the renal related consequences on blood pressure” (Paoli, 2014).
There are amino acids involved in the “production of urea, which could reduce blood pressure” (Paoli, 2014). In addition, they can also raise acidity levels and cause the blood pressure to rise. Obese individuals with renal difficulties are highly prone to hypertensive effects of amino acids.
KDs could also affect bone metabolism. Evidence suggests that a short-term ketogenic diets could negatively affect bone mass density and mechanical elements of bones whereas in human, long-term ketogenic diets in children who suffered “epilepsy may lead to a progressive reduction of bone mineral content” (Paoli, 2014).
Until recently, ketogenic diets have been regarded as effective approaches to obesity and overweight management through diets. However, current progresses in nutritional studies have highlighted several benefits and created public awareness about ketogenic diets. In human, many studies have identified that ketone bodies also provide brain energy just like glucose (Paoli et al., 2012; Poff et al., 2013).
Therefore, the utilisation of ketone bodies in the brain for energy could be a breakthrough development for obese individuals because hepatic release of ketone bodies when an individual fasts could act as an alternative energy source to glucose. This is essential to avoid a potential utilisation of glucose from muscles.
While ketogenic diets are clinically and experimentally sound and effective in obesity, overweight and epileptic management, its molecular mechanisms remain generally unclear and elusive. In addition, other studies have indicated that ketogenic diets could be superior to other anticonvulsants. Still, ketogenic diets have become effective for managing infantile spasms, as well as mood stabiliser among people with bipolar conditions (Brinkworth et al., 2009).
Given the benefits of ketogenic diets on the brain, it is recommended for individuals with depression or mania because of cerebral hypometabolism. At the same time, ketogenic diets also influence signal transmission in the nervous system by initiating alterations in the basic conditions of protein.
It may also affect gene expression in the brain cells and therefore, ketogenic diet is beneficial to the body in different ways. It can control epilepsy because ketone bodies can readily be transported in the brain through blood and move across many barriers. Therefore, several studies have supported ketogenic diets as alternatives for conditions related glucose.
Generally, researchers have highlighted that too much consumption of foods rich in high fat could result in obesity. Therefore, the main concern has been too much fatty foods enhance weight gain relative to low percentage of fat consumption. Generally, fats have high contents of calories than carbohydrates and it is believed that intake of high fat diets will result in high-energy intake.
On the contrary, recent studies have highlighted that ketogenic diets do not lead to weight gain. Instead, they act as therapies for people with overweight and obesity problems. Such studies have also established that diets rich in sugar are the main causes of many chronic conditions. In addition, they have also established sugar diets could facilitate aging processes.
Some studies have also shown that diets with high content of glycemic load (various foods with high glycemic index) have been linked to cardiovascular conditions, diabetes and other types of cancer. Glycemic index indicates various levels of glucose fluctuation after consumption of carbohydrate. Identification of carbohydrate based on this index is an effective means of predicting and understanding risk factor for heart conditions relative to the conventional way of grouping carbohydrate diets into simple or complex types.
Obviously, one main benefit of the ketogenic diet is that it enhances calorie consumption to be reduced significantly without initiating hunger. Therefore, ketogenic diets’ advantages could be extended to mitigate obesity and overweight across people of all ages.
Ketogenic diets have effects on metabolism and could produce significantly higher rates of fat oxidation than the normal rates. This could lead to reduced respiratory activities, including respiratory exchange ratio. A dietary manipulation (ketogenic diet) affects the exchange ratio and metabolic carbon dioxide output. This situation could result into “a decrease in arterial carbon dioxide partial pressure or of pulmonary ventilation, or of both” (Paoli et al., 2013). These suggestions have not been verified, but they could be useful in treating people with respiratory challenges. Nevertheless, these outcomes also require further studies.
Emerging evidence in the case of ketogenic diets
In the recent years, various studies have shown that ketogenic diets could help in managing various conditions, such as acne, cancer, polycystic ovary syndrome (PCOS), neurological diseases, Alzheimer’s disease, Parkinson’s disease, traumatic brain injuries and amyotrophic lateral sclerosis (Paoli, Rubini, Volek, & Grimaldi, 2013).
It is imperative to note that these results have been obtained from animal experiments and “direct experimentation and clinical trials in humans are still lacking now” (Paoli et al., 2013). Therefore, further studies are necessary for reviewing preliminary outcomes obtained from experiments with animals and results must be treated cautiously.
Conclusion
Short-term outcomes of ketogenic diets in management of obesity and overweight have been established as beneficial. On the other hand, long-term effects of such diets remain unclear. In fact, studies have established that obese people may regain significant amount of weight after the diet period. Such weight gains are compared to low energy diets. A period of ketogenic diets may help in significant weight reduction and could enhance “oxidation of fat metabolism and hence lower weight” (Paoli et al., 2012). In addition, certain kinds of diets may also enhance compliance to diet requirements and consumption.
On the contrary, ketogenic diets have negative effects on obese patients. For instance, further studies should focus on effects of such diets on renal functions. These studies should also investigate transition periods to regular diets. At the same time, effects on blood lipids and bone metabolism also require further investigations.
Ketogenic diet periods could range from “a minimum of two weeks to a maximum of 12 months” (Paoli, 2014). Overall, ketogenic diets could be effective interventions for managing obesity and overweight based on physicians’ recommendations and observation.
Recommendations
It is imperative to understand that increasing rates of obesity across people of all ages have led to new interventions. The concept of ketogenic diet, therefore, is relatively new, but has been identified as an appropriate intervention for obesity and overweight management. The Dietary Guidelines for Americans 2010 encourages consumption of “an eating pattern low in energy density to manage body weight” (Pérez-Escamilla et al., 2012).
Given evidence in the reviewed literature, there is a consistent consensus that ketogenic diets reduce overweight and help in obesity management on a short-term basis. In addition, such diets have shown positive correlation with enhanced adiposity. Overall, the research supports ketogenic diets for adults and children for managing obesity and overweight.
Second, further studies are required to ascertain long-term effects of ketogenic diets on obese and overweight individuals, including people with less than 30 BMI. Such studies are necessary because long-term outcomes of the intervention remain unclear and controversial. At the same time, it is also vital to investigate other health concerns that may arise from ketogenic diets.
Effective weight and obesity management programs require long-term commitments. This would result in healthy living, active life, appropriate diets and sustainable practices (Seagle et al., 2009).
Obese and overweight individuals require effective weight management programs, including diets (Vernon & Wortman, 2010). It is imperative to get physicians’ recommendations on diets before adopting any ketogenic diets. A physician’s recommendations are important because of the need to understand physiology in diets. Obese individuals should understand potential risks and physicians could offer the best remedies on how to optimise ketogenic diets for healthy outcomes (Rippe & Angelopoulos, 2012).
Physicians should evaluate their patients’ body weight and recommend suitable interventions alongside counselling. In this regard, physicians have the responsibility of assisting their patients to develop appropriate interventions, including weight loss and healthy diet programmes. In addition, they must monitor, evaluate and refer patients to other care providers. When evaluating the effectiveness of any weight management programme, it is necessary for patients and nurses to understand that the ultimate goal is weight loss alongside weight management for better health and improved outcomes.
Researchers should provide full accounts of ketogenic diets in their study outcomes. For instance, obese and overweight people should gain access to such information in details, guidelines and understand negative outcomes of ketogenic diets. While ketogenic diets are preferred to bariatric surgeries, physicians and researchers should also recommend appropriate alternatives to weight and obesity management, such as change in lifestyles and physical activities. The target group should understand physiology behind recommendations on diets and exercise.
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