Autophagy normally functions as
Macroautophagy is a catabolic process in which cytoplasmic material is sequestered in double-membrane autophagosomes that subsequently fuse with lysosomes for degradation. Under nutrient starvation autophagy recycles macromolecules to maintain essential metabolism and is therefore primarily a survival pathway. Only under extreme or prolonged stress does autophagy contribute to cell death.
Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)