The purpose of this study if to determine the specific contributions of energy intake and energy expenditure to changes in body weight and fat.

1. Changes in body weight and fat will be positively associated with increases in total energy intake.
2. Changes in body weight and fat will be positively associated with decreases in total energy expenditure.

Inclusion Criteria:

• BMI: 20-35 *Note : For participants that come to Orientation, we are allowing participants with a variance of 0.1 either way in the BMI range: 19.9 - 35.1

  • 21-35 years of age
  • Men and women
  • Email address
  • Access to a phone

Exclusion Criteria:

• Currently on medications to lose weight

  • >90th percentile on the Brief Symptom Inventory (BSI)
  • Planning to move from the Greater Columbia area in the next 15 months
  • Other medical, psychiatric or behavioral factors that in the judgment of the principal investigator may interfere with study participation or the ability to follow the intervention protocol.
  • Changed birth control status in past 3 months
  • Currently taking birth control but plan to stop taking it within the next 12 months or are planning to start taking birth control in the next 12 months
  • Planning to have weight loss surgery
  • Started or stopped smoking in the past 6 months
  • Blood pressure ≥ 150/90
  • Blood glucose ≥ 145 mg/dL @ orientation
  • Blood glucose ≥ 126 mg/dL @ B3
  • Total cholesterol ≥ 240 mg/dl with LDL-C ≥ 190 mg/dl or Triglyceride levels ≥ 300 mg/dL
  • Currently diagnosed with or taking medications for a major chronic health condition
  • Presence of an eating disorder
  • Currently participating in another study

A total of 400 participants will take part in the Energy Balance Study; 200 men and 200 women from 2 age groups: Ages 21-27 and Ages 28-35. A subsample of 200 will be randomized for doubly labeled water recruitment.