Can I track my weight in Foodnoms?

Not yet, but it's coming: weight tracking is part of the next major update to Foodnoms, including a weight chart, trends, weight goals, and Apple Health integration.

In the current version, if your calorie goal is calculated from your weight, you can keep your weight up to date from the "Resting Energy" screen, accessible when editing your Calorie goal (see "How do I create and edit goals?").