Epidemiologic evidence points to
obesity as a major risk factor for many
cancers, including
cancers of the breast, endometrium, colorectum, kidney, oesophagus and pancreas. Whether intentional
weight loss might reduce this excess risk is not yet proven. We searched the medical literature for studies reporting changes in
cancer risk following intentional
weight loss, and for studies reporting changes in
cancer-relevant risk factors of oestrogens,
sex hormone binding globulin (SHBG),
Insulin-like growth factor-I (
IGF-I),
IGF binding proteins and selected inflammatory markers [
C-reactive protein (CRP),
interleukin 6 (IL-6) and tumour
necrosis factor-α (TNF-α)]. Observational cohort studies and randomized controlled trials of both dietary interventions and
bariatric surgery all indicate fairly immediate reductions in
cancer incidence following intentional
weight loss. Oestrogen levels drop and SHBG levels increase coincident with intentional
weight loss, with about a one-third reduction in free
oestradiol to be expected from
a 10%
weight loss. CRP levels also drop substantially after
weight loss at about this same 3 : 1 ratio. Reductions in TNF-α and
IL-6 are consistently seen, but of a smaller magnitude, and
IGF-I and
IGFBP changes after
weight loss are small and inconsistent. Because both
cancer incidence and levels of circulating
cancer biomarkers drop fairly rapidly following
weight loss, intentional
weight loss may well lead to meaningful reductions in
cancer risk with a short latency time.