Does losing weight increase your lifespan?

Most studies show little effect of fat on life expectancy but the one below seems to.  So what is going on?  Easy.  There WAS  in fact a benefit from weight loss but it was very small. Which is what previous studies have shown

Association of Weight Loss Between Early Adulthood and Midlife With All-Cause Mortality Risk in the US

Wubin Xie et al.

Abstract

Importance:  Describing potential mortality risk reduction associated with weight loss between early adulthood and midlife is important for informing primary and secondary prevention efforts for obesity.

Objective:  To examine the risk of all-cause mortality among adults who lost weight between early adulthood and midlife compared with adults who were persistently obese over the same period.

Design, Setting, and Participants:  Combined repeated cross-sectional analysis was conducted using data from the National Health and Nutrition Examination Survey III (1988-1994) and continuous waves collected in 2-year cycles between 1999 and 2014. The data analysis was conducted from February 10, 2019, to April 20, 2020. Individuals aged 40 to 74 years at the time of survey (baseline) were included in the analyses (n = 24 205).

Exposures:  Weight history was assessed by self-reported weight at age 25 years, at 10 years before baseline (midlife: mean age, 44 years; interquartile range, 37-55), and measured weight at baseline. Body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) at each time was categorized as normal (18.5-24.9), overweight (25.0-29.9), and obese (≥30.0). Weight change patterns were assessed from age 25 years (early adulthood) to 10 years before baseline (midlife).

Main Outcomes and Measures:  Incident all-cause mortality using linked data from the National Death Index.

Results:  Of the 24 205 participants, 11 617 were women (49.0%) and 11 567 were non-Hispanic White (76.9%). The mean (SD) BMI was 29.0 (6.1) at baseline. During a mean (SD) follow-up of 10.7 (7.2) years, 5846 deaths occurred. Weight loss from obese to overweight was associated with a 54% (hazard ratio, 0.46; 95% CI, 0.27-0.77) reduction in mortality risk compared with individuals with stable obesity between early adulthood and midlife. An estimated 3.2% (95% CI, 1.6%-4.9%) of early deaths could have been avoided if those who maintained an obese BMI instead lost weight to an overweight BMI by midlife. Overall, an estimated 12.4% (95% CI, 8.1%-16.5%) of early deaths may be attributable to having weight in excess of the normal BMI range at any point between early and mid-adulthood.

Conclusions and Relevance:  In this study, weight loss from obesity to overweight between early adulthood through midlife appeared to be associated with a mortality risk reduction compared with persistent obesity.

SOURCE