In the USA, fundamentalist Christians and most people who consider themselves very religious tend to reject many biological facts (evolution of species, existence of genetic predispositions, genetics playing a major role in intelligence or temperament, etc.). I was wondering if this ignorance would lead them to make detrimental choices about their health and lifestyle, which would result, for instance in much higher rates of obesity. It turns out that it does, especially for women. Have a look at this study: Does Religion Increase the Prevalence and Incidence of Obesity in Adulthood? Note that it dates from 2006 and uses data from 1986 to 1994, so obesity rates are considerably higher today.

Feel free to read the study, but in short Baptists and other fundamentalist Christians have by far the highest rates of obesity, while Jews and non-Christians have 1% or less of obesity.

TABLE 2

PERCENT OBESE AT WAVE 1 AND WAVE 3 BY RELIGIOUS AFFILIATION: AMERICANS’ CHANGING LIVES, 1986–1994

Number of Cases, W1 Obesity
W1 W3
Baptist a 1,098 24% 30%
Fundamentalist Protestant b 250 18 22
Pietistic Protestant c 509 13 19
Nondenominational Protestant 166 5 5
Reformation-Era Protestant 453 9 9
Catholic 720 17 17
Nontraditionalist d 92 2 3
Jewish 59 1 1
Other non-Christian e 18 0.2 0.7
None 237 6 7
Total 3,602

a Includes Southern Baptist, North American Baptist, Fundamentalist Baptist.
b Includes Church of Christ, Pentecostal/Assembly of God, Church of God.
c Includes Methodist, Christian Church, African Methodist Episcopal.
d Includes Jehovah’s Witnesses, Mormon, Seventh Day Adventists, and Christian Scientist.
e Includes Muslim, Hindu, and Buddhist.