I think protein is the most thermogenic macronutrient? (Correct me if I'm wrong). ie. heat-producing. Digestion is a heat-producing event anyway, so maybe if you're eating a lot of protein it's just enhancing this effect. It happens to me too I don't really worry about it.
This could be really inaccurate, but anxiety and stress can produce "hot flashes". They can become more pronounced (possibly just easier to notice) after eating or exercising. Could be a different way of thinking about your hot flashes.