The main treatment effects according to body mass index category were that normal weight women in the intervention group gained less weight ( adjusted mean difference , 1.393 kg ; 95 % CI , 0.813-1 .972 kg ; P < .001 ) and were less likely to gain weight above the IOM recommendations ( odds ratio , 0.508 ; 95 % CI , 0.334-0 .774 ) than normal weight women who received standard care .