Food Insight have published a survey of just over a thousand young adults aged 18 to 34 to question them about their dietary habits over the previous year. The study was published in 2018.
At that time a third were following some sort of diet. 16% were following some sort of low carb diet. The most frequent eating pattern was intermittent fasting coming in at 10% of those questioned.
In order of frequency the dietary patterns were:
Intermittent fasting, Paleo (10%) Gluten free, Low carb, Mediterranean, Whole 30, High protein, Vegetarian or Vegan (about 5%), Weight loss plan, Cleanse, DASH diet, Ketogenic or high fat diet, and other.
My comment: my personal diet is a mixture of Gluten fee, Low carb, Mediterranean, High Protein and High fat so I can see that there is certainly room for difficulty in assigning your diet a category. There seems to be a lot of publicity over Vegan and Vegetarian diets and I was surprised that there were not more young people on these. I would imagine that it would depend where the sample was from and other demographic information.