LeBron James and Tim Tebow, Halle Berry and Gwyneth Paltrow, Kim and Kourtney Kardashian, Mick Jagger and Tim McGraw: All these celebrities are fans of the ketogenic diet.

Kim Kardashian says she lost 75 pounds of “baby weight” in a few months on the diet. Athletes cite better body composition and performance. Halle Berry, who has diabetes, uses it for blood sugar control. Gwyneth Paltrow’s website refers to its effects on brain fog and focus. And 74-year-old, rail-thin Mick Jagger may be hoping for the diet’s purported anti-aging effects.

All these claims are valid. The ketogenic diet has a broad range of benefits – it’s also a promising treatment for cancer, seizures, Alzheimer’s disease, and more. However, there’s confusion as to exactly what it is.

The goal is ketosis

The goal of the ketogenic diet is to shift the body away from using glucose, the preferred energy source, and into ketosis, or fat-burning mode. This is accomplished by drastically increasing fat and reducing carbohydrate and protein intake. In the absence of dietary carbs, glucose and glycogen (stored carbohydrates) are depleted, so the body reverts to its backup energy source: fat, which is broken down in the liver into ketone bodies and used as fuel.

The ketogenic diet is very effective for weight loss. When you’re in ketosis, the fat on your belly and hips is slowly siphoned off, converted to ketones, and burned for energy. Ketosis also curbs appetite, which makes weight loss all the easier. And as long as you’re getting adequate protein and doing strengthening exercises, the weight you lose will be fat, rather than lean muscle mass.

It’s also a terrific therapy for diabetes. In fact, before the discovery of insulin in 1920, a very-low-carbohydrate diet was the only treatment for type 1 diabetes. The ketogenic diet was also the primary treatment for epilepsy at that time. Although interest waned as anti-seizure drugs came on the market, it has made a comeback for epilepsy that doesn’t respond to drugs.

There is also increasing interest this diet for two of our most pressing and disturbing health challenges: cancer and Alzheimer's disease.

Starve cancer…

Nearly a century ago, Otto Warburg, a German physician and Nobel Laureate, discovered that unlike healthy cells, which create energy in the mitochondria in the presence of oxygen, cancer cells have markedly altered metabolism. They produce energy in a fermentation process without oxygen, utilizing extraordinary amounts of glucose. He theorized that cancer is a metabolic disease that could treated by depriving cancer cells of their energy source.

Today, cancer’s abnormal metabolism and huge appetite for glucose are widely recognized. The concept of targeting cancer by reducing its fuel source is also gaining ground – and the primary means of accomplishing this is a ketogenic diet. By dramatically lowering glucose and increasing ketones, which malignant cells cannot effectively use for energy, it literally “starves” tumors.

I am not suggesting the ketogenic diet cures cancer. However, studies demonstrate great potential as an adjunct therapy for slowing progression, increasing the efficacy of radiation and chemotherapy, and when used in conjunction with hyperbaric oxygen, reducing tumor growth and metastasis.

…Feed the brain

Ketogenic diets also hold promise for Alzheimer’s disease. Most of the current research targets amyloid, a toxic protein that damage the brains of patients with Alzheimer’s. However, the disease is also marked by reduced glucose metabolism – the brain simply doesn’t have the energy required for optimal function and repair.

A diseased brain may not be able to metabolize sugar, but it can run quite efficiently on ketones. This alternative energy source easily crosses the blood-brain barrier, supplies much-needed energy to poorly functioning brain cells – and may actually reverse symptoms of dementia.

In a three-month pilot trial, patients with Alzheimer’s who followed a ketogenic diet had significant improvements in cognitive function: a four-point average increase on a common testing scale, compared to the placebo group’s decline of two points. This is unprecedented. The diet worked better than any anti-amyloid drug ever tested.

The ketogenic diet also reduces inflammation in the brain, and preliminary research suggests it may also have a role in the treatment of Parkinson’s, ALS, and other devastating neurodegenerative diseases.

Classic ketogenic diet

The classic ketogenic diet – shown in scientific studies to control seizures, slow cancer progression, and improve symptoms of Alzheimer’s – is quite strict. Because the goal is to stay in ketosis, you must drastically reduce your carbohydrate intake. This means eliminating all sugars, grains, starchy vegetables, and fruits.

So what can you eat? Fat and lots of it – 75 percent of total calories should come from healthy fats and the remaining 25 percent from protein and carbohydrates. This means lots of avocados, coconut and olive oil, nuts and seeds, nut butters, eggs, chicken, red meat, butter, cheese, and full-fat Greek yogurt and cottage cheese. You can also eat some leafy greens along with cucumbers and other low-carb vegetables, but to remain in ketosis, total daily carb intake must be limited to 20-40 g.

Supplemental medium chain triglycerides (MCTs) give you a little wiggle room. MCTs, which are most abundant in coconut oil, are a type of fat that is rapidly converted into ketones. Because MCT oil adds both fat and ketones, it allows you eat a little more carbohydrate and still be in ketosis.

Some experts warn about dangers of this diet, but it’s really quite safe. The most common side effect is constipation, since it contains little fiber. It also lacks vitamins, minerals, and phytonutrients present in plant foods. However, these can be replenished with nutritional supplements.

Low carb, high fat, moderate protein

I’m not convinced that everybody on the ketogenic bandwagon is actually following such a strict regimen – and that’s okay. Less restrictive “modified keto diets” are also beneficial. They typically call for less fat (about 50 percent of total calories), more carbohydrates (50-100 g per day), and a wider variety of vegetables, some beans, and limited fruit.

A low-carb, high-fat and -protein diet may not keep you in ketosis 24/7 like the classic ketogenic diet, but it does facilitate weight loss and is a good option for anyone with obesity, diabetes, hypertension, lipid abnormalities, and other aspects of metabolic syndrome. Some evidence suggests that both approaches also support detoxification, boost antioxidant defenses, protect against cancer and dementia – and, in animal studies, even prolong lifespan.

No regimen is a perfect fit for everyone, but if you’re struggling with any of these conditions, the ketogenic diet is worth considering.

My recommendations

To learn more about the classic ketogenic diet for seizures, cancer, Alzheimer's, and other neurodegenerative diseases (4:1 ratio fats to protein and carbohydrates) visit The Charlie Foundation.

For details on a more lenient low-carb, higher-fat and -protein diets for weight loss, diabetes, metabolic syndrome, health maintenance, and disease prevention, check out the Paleolithic, modified Atkins, and Whole30 diets.