Based on the maps, it looks like gluten-free diets exploded in 2009, eating into searches about vegan and low-carb diets. Vox points to a number of factors, such as celebrity diet books, that made gluten free go viral.
Unsurprisingly, the methods by which people tortured themselves in the name of health were vastly different 10 years ago than they are today. In fact, the gluten-free diet is nowhere to be seen in top Google searches (that doesn't happen until 2006). Instead, people were more interested in eating organically, low carb diets, and the Atkins diet. Oh, and does the South Beach Diet ring a bell? That was huge in 2005, likely thanks to your mom, or a neighbor who swore by it, then subsequently gained all the weight back and stopped talking about it.