Analysis and Comparison of 3 Popular Weight Loss Plans

This paper was written in October, 2018 for an advanced nutritional sciences course.

          Weight loss is challenging to achieve and even more difficult to maintain. The body’s physiologic mechanisms favor weight regain and attempt to prevent weight loss.1,2Three current popular weight loss plans are the ketogenic diet, paleo diet, and Weight Watchers. These diets will be compared for their macronutrient content, weight loss and maintenance potential, and metabolic pathways, substrates, and hormones involved.

            The ketogenic diet is a high fat, low protein, and low carbohydrate diet. It was initially developed to treat refractory epilepsy. Although there is strong evidence that this diet can help reduce seizure frequency by greater than 50%, this diet has been promoted as a weight loss strategy because most patients do lose weight on this diet modification.3The original ketogenic diet has a 4:1 ratio of 4 grams of fat to every one gram of carbohydrate or protein.3As in the original ketogenic diet, in ketogenic diet studies for weight loss, greater than 90% of the macronutrient content is from fat.4,5During the first few weeks of the diet, evidence shows moderate weight loss occurring. The body must switch from using glucose for energy to using ketones. Because this mimics starvation, study participants initially lose weight. In mice, weight loss occurred, but once the body adapted (after about 10 weeks), the mice gained back the weight that was lost.4After week five of this study, the ketone body beta-hydroxybutyrate was elevated, indicating a ketogenic state. However, in the prolonged ketogenic state, these mice exhibited dyslipidemia, a proinflammatory state, and hepatic steatosis.4

Because ketosis is the goal, circulating levels of beta-hydroxybutyrate increase. In the liver and skeletal muscle cells, ketogenesis occurs. The pancreatic beta cells release significantly less insulin due to a decrease in dietary glucose. Before the discovery of insulin, the ketogenic diet was the first line of treatment for type II diabetes.6The adipocytes convert to lipolysis through the activation of hormone sensitive lipase.2Because this diet mimics prolonged starvation, the first fuel source for the brain and red blood cells is glucose through gluconeogenesis. As the ketogenic state is prolonged, the brain and red blood cells must switch to primarily using ketones from liver ketogenesis.2

The major hormonal profile change is driven by the ketogenic shift from using glucose for energy to using the fat-derived fuel source of ketone bodies. Weight loss occurs initially because the body thinks it is in starvation. It attempts to spare glucose for the brain and red blood cells, but as glucose diminishes, these organs must use primarily ketones. Pancreatic beta cells produce less insulin, so glucagon is the predominant hormone. Glucagon is a catabolic hormone, so lipolysis and proteolysis are favored.2This creates an anorexigenic state. Once the body adapts to the ketogenic diet, weight loss does not continue and a long-term ketogenic diet can lead to glucose intolerance.4Another long-term potential side effect of this diet is metabolic acidosis, which is unfavorable due to pH disruptions and respiratory and renal compensations.2,3Although the ketogenic diet can result in short-term weight loss, the effects on pancreatic endocrine cells and metabolism of glucose long-term are not beneficial.

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To continue reading about the paleo diet and Weight Watchers, please contact me for the full paper.