How can a diet that pushes butter, red meat and bacon, and eliminates complex carbohydrates like fruits, vegetables, and whole grains, be a good thing? I’m frequently asked about the ketogenic (keto) diet. Admittedly, I began my investigation with a distinctly negative bias.

Back in the 1920s, researchers observed that children with epilepsy improved on this type of diet, and it has remained in the medical textbooks ever since. There is now speculation that other groups of people might benefit from it, including those with neurodegenerative disorders such as multiple sclerosis, Parkinson’s and Alzheimer’s disease, and even those with traumatic brain injuries.

The keto diet allows very few or no carbohydrates, which are the body’s main source of energy. The body is then forced into a state of ketosis, where fat is burned for energy instead of carbohydrates. The keto diet includes large amounts of high-fat foods, including red meat, avocado, coconut milk, oils, nuts and nut butter, bacon, egg yolks, butter and cheese. It also includes fish and seafood, low-carb vegetables, meat, poultry, and plain yogurt. A very small quantity of leafy greens, broccoli, asparagus, cucumber, celery, tomatoes, peppers, mushrooms and zucchini are allowed.

Excluded foods include fruit, bread, pasta, legumes, beans, starchy vegetables like sweet potatoes, vegetables like winter squash, beets, or carrots, most processed foods, and anything with added sugar. Calories break down to about 75% fat, 20% protein, and 5% carbohydrate. This is dramatically different from the standard American diet, where the proportions are closer to 50% carbohydrates, 30% fats, and 20% protein.

Surprisingly, both research and anecdotal evidence have shown that this high fat diet can indeed be effective for weight loss. The body is forced to burn fat for energy. In addition, eating high fat foods can help minimize cravings and increase the feeling of being full.

The keto diet is also recognized for helping to control insulin sensitivity and release, which plays a vital role in controlling diabetes. When carbohydrates are eliminated, an overload of insulin is avoided, and more balanced blood sugar levels result.

By now, my readers should be expecting to see the word “however.”

· HOWEVER, our brains use sugar to perform. Without carbohydrates, glucose doesn’t enter the blood stream, resulting in a decline in brain function.

· HOWEVER, starvation due to a prolonged lack of carbohydrates can lead to the body losing muscle and energy. Note that once the body enters starvation mode, it can actually be more difficult to shed weight.

· HOWEVER, athletes avoid the keto diet. Low carbohydrate and high fat diets have been shown to do a poor job at feeding the muscles, reducing muscle mass and peak sports performance.

· HOWEVER, while studies do show that consumption of large amounts of saturated fats can actually level out cholesterol levels (temporarily), this diet can ultimately result in much higher blood cholesterol, which can cause far more harm than good, particularly to the heart.

Studies have not yet examined the long-term possible negative impacts on the heart, kidneys, nutritional deficiencies, hydration, cholesterol, etc. The keto diet is recommended only for short-term use, generally for a maximum of 12 weeks. It is not a good idea for the long run, is very difficult to maintain, and doesn’t offer a good option for a full lifestyle change.

I do find the ketogenic diet fascinating because it forces the body to digest fat, thereby targeting body fat stores, resulting in weight loss. The data on treating certain neurodegenerative diseases is promising, and is undergoing further study. The data on diabetes control is also noteworthy. But remember that we need carbohydrates to fuel our brains and our bodies.

The best diet in the long-term is one that builds healthy and sustainable habits. If you are considering the keto diet, I urge you to evaluate with your doctor whether it is appropriate for your own unique health profile.

Dr. Alan Frischer is former chief of staff and former chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 8301 E. Florence Ave., Suite 100, Downey, CA 90240.