Is it possible to reverse diffuse hair loss due to nutritional deficiency?

My scalp started thinning especially at the crown and hair temples when I started eating junk food and lost 20kg in 2 months. Its been 3 years now and my hair seems to have the exact same pattern. Whenever I eat healthy for a week, clean diet, I see my hair get really thick especially crown and hair temples but still visibly thin compared to the whole scalp. If I go on a healthy diet and no stress would my hair grow back. I went through a bad break up which resulted in anxiety and stress.