**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** OBESITY AFFECTS 40% OF U.S. ADULTS (20-39 YEARS) AND 22% OF CHILDREN (12-19 YEARS) AND HAS A $173 BILLION/YEAR HEALTHCARE COST. OVERNUTRITION CONTRIBUTES TO OBESITY; HOWEVER, SPECIFIC NUTRITIONAL STRATEGIES FOR FEMALES ARE LACKING, DESPITE EXPERIENCING HIGHER RATES OF OBESITY. WOMEN AND GIRLS HAVE DIFFERENT HORMONES THAN THEIR MALE COUNTERPARTS, SUPPORTING THE NEED FOR SEX-SPECIFIC NUTRITIONAL RECOMMENDATIONS AND CONSIDERATIONS TO PREVENT OBESITY IN THIS POPULATION. THIS PROPOSAL INVESTIGATES THE RELATIONSHIPS BETWEEN THE DEVELOPMENT STAGE, HORMONES, AND NUTRITION'S CONTRIBUTION TO OBESITY DURING THE POSTPARTUM AND ADOLESCENT PERIODS OF FEMALES.BREAST MILK AND BREASTFEEDING ARE GOOD FOR BABIES AND MOMS. THE MAJORITY (83.2%) OF NEW MOTHERS GIVE NEWBORNS BREASTMILK. HOWEVER, THAT PERCENTAGE DECREASES IN THE FIRST FEW WEEKS OF THE POSTPARTUM PERIOD, DESPITE LACTATION'S BENEFITS. HOW BREASTFEEDING HELPS THE MOTHER NEEDS TO BE BETTER DEFINED. THIS PROPOSAL'S FIRST OBJECTIVE WILL USE STATE-OF-THE-ART TECHNIQUES TO UNDERSTAND HOW THE HORMONES INSULIN AND PROLACTIN CHANGE THE FAT IN BREAST MILK. THE FAT IN HUMAN MILK IS ESSENTIAL FOR THE BABY'S GROWTH AND BRAIN DEVELOPMENT. THEREFORE, IT IS VITAL TO UNDERSTAND HOW CHANGES IN THE MOTHER'S HEALTH MAY AFFECT THE MILK BEING FED TO HER INFANT.MANY REPRODUCTIVE-ASSOCIATED DISORDERS AFFECT WOMEN. THE MOST COMMON REPRODUCTIVE DISORDERIS POLYCYSTIC OVARY SYNDROME. THIS SYNDROMEAFFECTS UP TO 1 IN 5 FEMALES OF REPRODUCTIVE AGE AND IS CHARACTERIZED BY HIGH TESTOSTERONE CONCENTRATIONS. THIS SYNDROME OFTEN PRESENTS DURING PUBERTY AND INCREASES THE LIKELIHOOD OF DEVELOPING OBESITY, TYPE 2 DIABETES, AND FATTY LIVER DISEASE. THE SECOND OBJECTIVE WILL DETERMINE IF DECREASING DIETARY SUGARS AND IMPROVING THE DIET QUALITY OF ADOLESCENT GIRLS WILL RESULT IN WEIGHT LOSS AND IMPROVED HEALTH. GIVEN THE INCREASED RISK FOR OBESITY-ASSOCIATED CONDITIONS WITH POLYCYSTIC OVARY SYNDROME AND THE AGE OF ONSET, FINDING NONPHARMACEUTICAL INTERVENTIONS TO TREAT AND PREVENTCOMORBIDITIES IS IMPORTANT.THE COMBINATION OF THESE OBJECTIVES WILL LEAD TO A BETTER UNDERSTANDING OF THE EFFECTS OF OVERNUTRITION AND ITS ROLE IN OBESITY-ASSOCIATED RISKS. BY DOING THESE STUDIES, KNOWLEDGE WILL BE GAINED ABOUT HOW NUTRITION AND HORMONES AFFECT OBESITY IN GIRLS AND WOMEN IN THE U.S. THIS CAN HELP WITH THE DEVELOPMENT OF BETTER DIET RECOMMENDATIONS TO KEEP PEOPLE HEALTHY.