Hi Mez. Welcome to the forum. I'm sorry that you find yourself here but I hope you find it as warm & supportive as I have. We also have a lot of laughs!
I requested and saw a dietician early on in my diagnosis. I needed to lose a lot of weight to be a) healthier and b) to reduce the risk factors for my bilateral mastectomy & reconstruction. I had already lost five kilos and have now lost 25kgs. In my darkest days, tossing and turning at night, sometimes focussing on my weight loss helped me through. It certainly gave my brain a break from thinking about cancer!
I found working with a dietician to be excellent. You get five subsidised visits if you get a care plan from your GP. My dietician understood all the chemotherapy issues very well. Broadly, her advice was to eat to the normal recommendations, fruit, veg, wholegrains, nuts & legumes and lean meats. However during chemo she increased my protein intake by a lot to combat muscle loss. She advised to reduce the carbs as well. A small amount of healthy carbs were fine.
I don't know if you are having chemotherapy. My oncologist said the aim during chemo is to maintain your weight. However she was happy for me to lose as long as it waa done safely and steadily. As chemo wiped out my appetite for at least 10 days in each cycle it wasn't too hard!
I am not a doctor and would strongly advise you to discuss any diet plans with your oncologist and GP. If your cancer is ER+ it can be fed small amounts of estrogen from your body fat. I don't know if a high fat diet influences this. As with all things breast cancer, it's wise to check with your doctors before adding or removing anything to your diet and health regime.
Let us know how you get one. Big hug, K xox