CNN  — 

People were curious about the keto diet, ALS and endometriosis in 2018.

Those are just a few of the health-related topics that had Internet surfers in the United States turning to Dr. Google with questions this year, according to a top 10 list from the search engine giant.

The data, based on search terms, was collected from January to mid-December.

Last year, some of the top health-related questions searched on Google included what causes hiccups, how to stop snoring, how long flu lasts and what is lupus. Some of the top health-related questions on Google in 2016 were related to Zika, traumatic brain injuries and cupping.

Here’s a look at the top trending health-related questions for this year – along with their answers.

1. What is the keto diet?

The ketogenic or “keto” diet topped the list of trending health-related questions searched on Google this year.

The diet is high in fats, moderate in proteins and very low in carbs. Its aim is to put the body into “ketosis,” when it breaks down both ingested and stored body fat into ketones, which it uses as energy.

The keto diet has grown in popularity, and many people tout its effectiveness for weight loss, but in January, US News and World Report ranked it last on its list of best diets.

The experts on the US News and World Report panel were concerned about the diet’s high fat content – about 70% of daily calorie intake – as well as unusually low carbohydrate levels: only 15 to 20 net carbs a day. The 2015-20 dietary guidelines for Americans suggest that 45% to 65% of daily calories come from carbs and less than 10% from saturated fat.

“When you are on the keto diet, you drastically cut your carbs to only 20 per day. That’s less than one apple!” said nutritionist Lisa Drayer, a CNN contributor.

For some, “the keto diet is just not sustainable over the long term. It doesn’t teach you how to acquire healthy eating habits,” she said. “It’s good for a quick fix, but most people I know can hardly give up pasta and bread, let alone beans and fruit.”

2. What is ALS?

Amyotrophic lateral sclerosis or ALS came in second on the list of trending health-related questions for 2018.

This progressive nervous system disease attacks nerve cells in your brain and spinal cord. Physicist Stephen Hawking, perhaps the most famous ALS patient, died of the disease in March.

Hawking, who was diagnosed with the condition in 1963, lived with it for more than 50 years – a remarkably long time for an ALS patient. The disease left him paralyzed and completely dependent on others and technology for everything: bathing, dressing, eating, mobility and speech. He was able to move only a few fingers on one hand.

ALS is also called Lou Gehrig’s disease, after the New York Yankees player who retired in 1939 because of the condition. Other notable people who had the disease are actor David Niven, NBA Hall of Famer George Yardley and jazz musician Charles Mingus.

Little is known about the causes of the disease, and there is no cure. The condition is slightly more common in men than women.

3. What is endometriosis?

Endometriosis was the third topic that had people Googling this year. The condition occurs when tissue that normally lines the uterus grows outside of the uterus, which can be painful and lead to infertility.

More than 11% of women in the United States may experience endometriosis; one of them is Lena Dunham, star and producer of the HBO series “Girls.”

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Dunham revealed in February that she had undergone a hysterectomy due to her pain from endometriosis. In March, four months after her procedure, Dunham said she was recovering and wants to dedicate her life to raising more awareness around endometriosis.

“Anything that is caught in the shadows like endometriosis, that leaves women feeling lonely, that leaves women feeling less than, that is what I want to devote myself to,” she said. “Endometriosis is one of the things I really want to talk about, and I want to talk about everything that is stuck in the shadows for women that they don’t feel they can discuss.”

The top 10 questions on health

What other questions did people search on Google this year? The full top 10 list included questions about the flu, heartburn and high blood pressure:

  1. What is the keto diet?
  2. What is ALS disease?
  3. What is endometriosis?
  4. How long does weed stay in your urine?
  5. How long does the flu last?
  6. How long is the flu contagious?
  7. When does implantation bleeding occur?
  8. Why am I always tired?
  9. What does heartburn feel like?
  10. What causes high blood pressure?

CNN’s Sandee LaMotte, Euan McKirdy and Chloe Melas contributed to this report.