This trial studies how well a lifestyle intervention works in reducing breast cancer risk through changing body composition and decreasing inflammation in normal weight women. This trial may help researchers learn more about diet and exercise programs designed to decrease body fat in postmenopausal women who are of normal weight but have an elevated risk of breast cancer because of excess body fat.

PRIMARY OBJECTIVE:

I. Evaluate the feasibility of a diet and exercise intervention to decrease body fat in postmenopausal women with normal body mass index (BMI) but high body fat (trunk fat mass 9.4 kg, the 50th percentile of normal BMI women in the Women's Health Initiative [WHI]).

SECONDARY OBJECTIVE:

I. Assess preliminary efficacy of the intervention by evaluating the post-intervention differences between the intervention and control groups in:

IIa. Circulating markers of inflammation and metabolic dysfunction linked to both excess adiposity and breast cancer (high sensitivity C-reactive protein [hsCRP], fasting insulin, leptin, IL-6, triglycerides, sex hormone binding globulin [SHBG], adiponectin, and high density lipoprotein [HDL] cholesterol).

IIb. Body composition body fat, trunk fat mass, fat mass, lean mass, fat-free mass).

EXPLORATORY OBJECTIVE:

I. Exploratory outcomes include fitness (oxygen consumption VO2 peak, sit-to-stand test), behavior (physical activity, energy intake, macronutrient consumption), and quality of life (global health-related quality of life, physical functioning, sleep, menopausal symptoms).

OUTLINE: Participants are randomized to 1 of 2 groups.

GROUP I: Participants complete lifestyle intervention consisting of 1-3 sets of high-resistance circuit training sessions per week, up to 150 minutes of aerobic training per week, and diet recommendations from a health coach or registered dietitian twice per week for 16 weeks.

GROUP II: Participants are placed on a wait-list and then complete lifestyle intervention after 4 months.

Inclusion Criteria:

• Age 50-69 years old
• Postmenopausal woman (absence of menstruation for at least one year, or history of bilateral oophorectomy)
• Self-reported height and weight indicating a BMI >= 18.5 and < 25 kg/m^2
• No contraindications to exercise (either no positive responses on the Physical Activity Readiness Questionnaire, or clearance from a health care provider certifying that the participant is healthy enough to exercise)
• No history of invasive cancer, other than non-melanoma skin cancer
• No history of renal disease
• Able to walk without an assistive device
• Not within 3 months of major surgery
• Able to speak/read/write in English
• Has internet access on a computer or mobile device
• A trunk fat mass >= 9.4 kg as indicated by a dual x-ray absorptiometry (DXA) scan
• Height and weight indicating a BMI of >= 18.5 and < 25 kg/m^2 verified at the screening visit

Exclusion Criteria:

• MD Anderson employees that report to the principal investigator of this study
• Participants that cannot engage in the exercise program for more than three weeks during the study period
• Participants that are currently doing strength exercises that work all major muscle groups (defined as: participants who complete more than 16 repetitions per exercise in their current resistance training regimen, or who don't find their last 1-2 reps to be difficult in their current regimen, or who increase the weight in their current routine).

4 years