We probably all know someone who’s lost weight and feels amazing on the ketogenic diet. There’s a good deal of science behind it, and I’ve tried it myself, so let’s take a deeper look at what a keto diet is, what conditions it might benefit, and any potential downsides.
What is the Ketogenic (Keto) Diet?
It’s a very low-carbohydrate, high-fat diet designed to put the body into a state of ketosis. Our body naturally goes into ketosis whenever there isn’t enough glucose to use for fuel. Most glucose comes from carbs in the diet, but roughly 50% of protein can also be turned into glucose. In ketosis, your body makes ketones from fat and uses them for energy instead of glucose.
Generally, to attain ketosis, you need to do two things: 1) Eat less than 50 grams of carbs per day (by comparison, although there’s no strict definition, a low-carb diet is under 100-150 grams per day), and 2) get at least 70% of your calories from fat. Medium-chain triglycerides (MCT), like those found in coconut oil, yield more ketones per calorie than long-chain triglycerides (LCTs). This means less total fat is needed when including MCT in the diet, which allows a bit more flexibility in carbohydrate and protein intake. Protein is limited to 0.8 grams per kilogram of body weight (or 0.36 g/lb), as the body is able to make glucose from it.
When you consider that one banana is about 20-30 grams of carbohydrate, you can appreciate how difficult it can be to achieve and remain in ketosis long-term. In addition, some people experience “keto flu” (low energy, brain fog, sore muscles, nausea, stomachache, trouble sleeping) until their bodies adjust to the diet.
What Is It Helpful For?
The ketogenic diet has been used to treat drug-resistant epilepsy, particularly in kids, since 1921.1 There are four ketogenic diets recognized by the International Ketogenic Diet Study Group for the treatment of pediatric seizures. These include the classic LCT ketogenic diet, MCT ketogenic diet, Modified Atkins Diet (MAD) and Low Glycemic Index Treatment (LGIT). The last two may be as effective as the more classic LCT and MCT diets and better tolerated. Click here to read an excellent review on the keto diet and seizures. People living with seizures, should consult with their health care provider first, and be closely monitored by a qualified dietitian.
I have a family member who lost more than 40 pounds in less than three months on a keto diet. He reported having more energy, less hunger, and better mental focus while on the diet. He’s not alone. Numerous studies show that a ketogenic diet is more effective for weight loss than a low-fat diet in people with obesity.2 One study found weight loss was 2.2 times greater for those on a ketogenic diet, compared with those on a low-fat, calorie-restricted diet.3 People often report feeling less hungry when they’re in ketosis. Fats, particularly MCTs, have a beneficial effect on satiety via the release of appetite-suppressing hormones and slower gastric emptying.4
Type 2 Diabetes
We’re seeing an explosion in type-2 diabetes globally, not just the United States. Driven by interrelated factors – high glycemic load diet (e.g., sugar, pasta, pastries), lack of physical activity, high-stress lifestyle, dysbiosis, environmental factors, obesity – more than 100 million Americans now have diabetes or prediabetes.5 A low glycemic load diet is crucial for preventing blood sugar spikes and regulating insulin response. There is no question that restricting carbohydrates to 5-10% of calories will help with blood sugar regulation. Research suggests that a keto diet improves insulin sensitivity in people with type 2 diabetes, as well as helps with weight loss.6 Keto diets are not recommended for those with type-1 diabetes or kidney disease.
Weight loss on the keto diet may help lower risk factors for cardiovascular disease. A small but well-done 90-day study found that the keto diet (70-75% fat, 20-25% protein, 5% carbohydrates) significantly reduced body weight (average 19.8 pounds), blood pressure (~reduction 11 pts systolic and 7 points diastolic); HbA1C (from an average of 8.9% to 5.6%); and significantly lowered triglycerides and raised HDL-C in women (ages 18-45) with type-2 diabetes and features of metabolic syndrome.7 While there was no change in LDL-C, it is important to note that the TG : HDL ratio has a stronger correlation to heart disease than LDL-C. Longer-term research with a greater number of participants is necessary to determine if the ketogenic diet, over time, actually reduces cardiovascular disease but these early data are intriguing.
Some studies suggest the ketogenic diet may support cancer therapy by starving cancer cells of glucose.8 A keto diet has been used to reduce fasting insulin and insulin-growth-factor (IGF) levels in women with ovarian or endometrial cancer.9 Elevated levels of insulin and IGF can increase tumor growth and aggressiveness. But some research suggests that certain types of cancer cells may use ketones for fuel.10 While the verdict is still out when it comes to the keto diet and cancer, rotating a keto diet, low-glycemic load diet, and vegetarian diet for eight weeks at a time might be an option for those interested in this approach.
The keto diet can be beneficial for weight loss and improving numerous metabolic parameters but for some people, the adjustment period can be hard. And you need to regularly monitor ketones in your urine to ensure you are in ketosis.
If one decides to undertake a keto diet, it is important to emphasize “healthier” food choices. For fats: emphasize olive oil, MCT oil, nuts, seeds, avocados, with moderate amounts of nut butters, butter, and cheese. For protein: fish (e.g., wild-caught salmon, sardines), lean meats, eggs, tofu, mushrooms; and avoid processed meats. For carbohydrates: incorporate unlimited amounts of non-starchy vegetables (e.g., broccoli, cauliflower, green beans, artichokes, cabbage, celery, salad greens), while eliminating potatoes, grains, desserts, and sugary beverages. Fruits: emphasize tomatoes, peppers, cucumber, eggplants, olives, avocados, ½ cup berries (day), while eliminating essentially all the rest.
You should consider taking a multivitamin supplement with additional calcium/magnesium, as it is easy to fall short of certain nutrients while on the keto diet.
Safety Tips for the Keto Diet
Stay hydrated! Especially during the first two weeks of the diet to reduce the risk of “keto flu.” During the first 2 weeks, significant increases in urine production may require adjustment of certain medications being taken for high blood pressure, heart failure, and diabetes.11 If you have a chronic or serious medical condition, talk with your healthcare provider or dietitian if considering a keto diet. Keto diets are not appropriate for pregnant and breastfeeding women.
For those who do not want to do a full-blown keto diet, intermittent fasting can also put you in ketosis if limiting food intake to a 6-hour window within each 24-hour day.12
Something that is rarely discussed but should be considered is that high fat intake can lead to increased adsorption of highly toxic lipophiles such as dioxins, PCBs, and chlorinated pesticides. To reduce PCB exposure, look for wild-caught Alaskan salmon, Pacific wild-caught sardines, farmed rainbow trout, and canned light tuna that has the Marine Stewardship Council (MSC) label, which indicates the tuna is less than 20 pounds and therefore much lower in mercury and PCBs. Choose organic produce to reduce pesticide exposure and lean meats to reduce dioxin exposure.