The Ketogenic Diet: Is there truth behind the hype?

Komal Motwani, MD

Being obese, or being grossly overweight, has become a national epidemic, with 40 percent of U.S. adults and 19 percent of U.S. children classified as obese. Furthermore, according to a recent study from the Harvard T.H. Chan School of Public Health, more than 50 percent of today’s children are expected to be obese by age 35.

This epidemic of obesity and our ongoing efforts as a society to identify ways to lose weight have led us to different approaches to address the issue, including medications, surgery and diet. One approach, the ketogenic diet, which features a high-fat, lowcarbohydrate regimen, is currently a popular option. But is it a fad of the day or does it offer a valid approach to weight management — or, more specifically, allow weight loss?

The ketogenic diet approach is based on an intake regimen of more fat, moderate protein and low-carbohydrate meal content. This approach is meant to put the body in a metabolic state called “nutritional ketosis” whereby the liver bypasses using glucose (blood sugar) as its main fuel, instead converting fatty acids into ketone bodies that act as the body’s fuel for energy. It was originally conceived in the 1920s to lessen seizure activity in those diagnosed with epilepsy.

While carbohydrates – which the body breaks down or converts into glucose for energy – comprise 55 percent of the typical American diet (200-250 grams per day), the ketogenic diet only allows 20 to 50 grams of daily carbohydrates, derived mainly from non-starchy vegetables such as asparagus, baby corn, beets, beans (green, wax, Italian), broccoli, cauliflower, eggplant, onions, salad greens and squash. The theory behind the reduction in dietary sugars is that there subsequently should be a lower secretion of insulin, a hormone produced by the pancreas to regulate glucose in the blood and – in turn – a decrease in insulin resistance, a condition that occurs when cells of the body don’t respond properly to the hormone insulin, causing glucose (sugar) to build up in the blood. The high levels of insulin in the body contribute to the development of type 2 diabetes and obesity.

People on a ketogenic diet often experience rapid weight loss, up to 10 pounds in 2 weeks. The initial few pounds are due to losing water, which is otherwise required to store excess carbohydrates in the liver as glycogen, a large molecule that is the predominant storage form of glucose and carbohydrates in the body. However, the overall amount of weight loss experienced depends on many factors including age, gender, ethnicity, level of physical activity, pre-dietary body fat and lean muscle mass, as well as the number of calories decreased once on a ketogenic diet. In a review of 13 studies comparing lowcarbohydrate diets with ketogenic diets, the conclusion was that there was greater weight loss in those on the ketogenic diet. However, looking more closely at the results, the “significant difference” was 1 kilogram, the equivalent of 2.2 pounds.

It’s important to remember that maintaining weight loss is an even harder challenge than achieving it. Once your body begins to sense you are losing weight, it triggers a series of physiological adaptations to preserve your weight, such as decreasing your metabolic rate (slowing your metabolism, the process of biochemically converting calories into energy required for body functions) and increasing your sense of hunger, with a tendency to restore body fat. Whereas lowfat diets were found to slow metabolism by more than 400 kilocalories per day, an extremely low-carb diet resulted in no significant decrease in metabolic rate. So a ketogenic diet should offer a better ability to keep weight off.

Additionally, people feel less hungry on a ketogenic diet, presumably due to the hunger-satisfying properties of fat and protein. Additionally, changes in appetite-regulating hormones and the direct hunger-decreasing role of ketone bodies are possible factors. Combined, these features not only help, but also maintain weight loss.

And a ketogenic diet is reported as more heart-healthy, despite the higher fat intake. People on ketogenic diets lose more deep (intra-abdominal fat) than low-fat dieters. Ketogenic diets increase high-density lipoprotein (HDL or good cholesterol) and lower triglycerides (sugar fats), abdominal girth/waist size and blood pressure. Moreover, a ketogenic diet can lead to improvement in diabetes-related blood sugar control as suggested by decreases in HbA1C, a blood test that assesses the control of blood sugar over the previous three months. Ketogenic diets have even been reported to help in decreasing the need for blood-sugar control medications used in the treatment of diabetes, potentially allowing some patients to come off medications within a year after starting the diet.

This is all good news, but does a ketogenic diet pose any concerns?

Of course, the answer is yes. On the negative side, some people on this diet experience an increase in low-density lipoprotein (LDL or bad cholesterol). Eating more unsaturated, rather than saturated, fat could possibly help decrease some of the rise in LDL levels, but the ideal ketogenic diet fat composition is unclear at this point.

The most common side effect of this type of diet includes a constellation of symptoms called “keto flu” which can last as little as a few days but also up to several weeks. Symptoms include lightheadedness, dizziness, fatigue, difficulty exercising, poor sleep and constipation. Maintaining a good electrolyte (sodium, potassium and magnesium) balance on this diet by consuming protein intake from whole foods such as cooked grains and hummus, rather than purified protein products, can help diminish some of these effects.

Not everyone needs an equal amount of carbohydrate restrictions to lose weight. Expert individualized advice is recommended to determine if you’re a good who candidate for this diet and also to establish individual goals. Most people with insulin resistance benefit from strict carbohydrates restriction. However, the carb intake and diabetes medications may need continued monitoring and adjustment to prevent low blood sugar, especially in those individuals with diabetes who are using insulin or other diabetes medications. Similarly, blood pressure medications may also need monitoring for possible adjustment.

Once a weight goal is achieved, some people may be able to add a limited amount of carbohydrates back in their diet while still maintaining their lower weight. This will vary based on individual carbohydrate tolerance or one’s ability to metabolize carbohydrates.

Overall, a ketogenic diet is generally considered safe when supervised by a medical professional and has been successfully used for sustained weight loss. However, it needs to be implemented with a dedicated program after an assessment of individual variations, with continued monitoring of diabetes, blood pressure and cholesterol parameters and medications. Large-scale trials are needed to further assess the diet for better understanding of its benefits in the long run.

The Ketogenic Diet In a Nutshell


  • Helps lose and maintain weight loss
  • Decreases appetite
  • Improves HDL and triglycerides
  • Lowers blood pressure


  • Keto flu
  • May increase LDL/bad cholesterol
  • Not a do-it-yourself diet
  • Not for everyone


  • May need dietary adjustments time to time
  • Increased risk for low blood sugar when on diabetes medicines
  • Needs diabetes, blood pressure and cholesterol medication adjustment