Sarcopenia is drastically accelerated from radiation because of chronic oxidative stress and damage to neuromuscular junctions that then inhibit the natural autosynaptic process of motor neurons which begins the decline.

Cholesterol, particularly LDL levels > 100, increases the risk of carotid accumulation of cholesterol plaque that contributes to stroke out, post radiation. Oxidative stress speeds up the destruction of the artery walls which then prohibits efficient vasodilation/constriction to keep plaque from accumulating, whether it is calcium or cholesterol plaque.

The missing piece in viewing the physical decline is the restricted blood flow that creates atrophy, muscle weakness and further catabolic destruction. Without addressing the blood flow, aging accelerates.

If you are able to eat, supplementary protein powders are mostly beneficial for feeding muslces during exercise activties. There are many high-protein, low fat or at least low "bad" fat options. Lipids or fats are essential to the nerve myelin and other neuromuscular function and a pure low-fat diet, post radiation, is not a good option.

Without knowing more history, conventional or standard nutrition guidelines are only a starting point and I don't believe any two people are the same.

SCC Stage IV, BOT, T2N2bM0
Cisplatin/5FU x 3, 40 days radiation
Diagnosis 07/21/03 tx completed 10/08/03
Post Radiation Lower Motor Neuron Syndrome 3/08.
Cervical Spinal Stenosis 01/11
Cervical Myelitis 09/12
Thoracic Paraplegia 10/12
Dysautonomia 11/12
Hospice care 09/12-01/13.
COPD 01/14
Intermittent CHF 6/15
Feeding tube NPO 03/16
VFI 12/2016
ORN 12/2017
Cardiac Event 06/2018
Bilateral VFI 01/2021
Thoracotomy Bilobectomy 01/2022
Bilateral VFI 05/2022
Total Laryngectomy 01/2023