The investigators plan to implement a novel limited RED (high-energy-dense) food variety prescription within a 18-month FBT to examine its effect on 18-month body mass index (BMI). This will be the first randomized control trial to examine how habituation rate, assessed via salivary habituation, mediates reduction in RED food intake, overall energy intake, and reductions in BMI over time, as well as if baseline habituation rate is a behavioral phenotype that moderates BMI outcomes. One hundred fifty-six children aged 8 to 12 years at > 85th percentile BMI will be randomized to one of two, 18-month interventions compared in our 6-month pilot study: FBT (family-based behavioral obesity treatment) or FBT+Variety. Child and adult caregiver assessments will occur at 0, 6, 12, and 18 months on anthropometrics, dietary intake (RED food variety, energy, and diet quality), habituation, and physical activity.

Identifying successful methods for reducing long-term energy intake continues to be a challenge in obesity treatment. Basic behavioral research has found that the rate of habituation (i.e., rate of reduction in physiological and behavioral responding) to food is related to amount of food consumed, and faster habituation rates reduce food intake. The rate of habituation to food can be accelerated when variety in foods is limited, producing decreased intake. Thus, a dietary prescription that limits variety of high-energy-dense (HED) foods may boost ability to reduce long-term energy intake, enhancing long-term weight loss.

Furthermore, habituation rates to food show large individual variability. For example, individuals with overweight habituate slower to food than individuals with a healthy weight, and slower habituation rates predict greater increases in child standardized body mass index (ZBMI). Thus, slower habituation rates to food may be a behavioral phenotype for increased risk of suboptimal weight outcomes. Obesity interventions that accelerate habituation to food may then be more beneficial for those with this behavioral phenotype.

The investigators have been conducting a line of translational research that applies habituation theory to obesity treatment involving: 1) studies systematically testing basic concepts to better inform intervention development; 2) "proof-of-concept" testing; and 3) efficacy trials. The long-term goal of this research is to develop a dietary prescription that harnesses habituation as a mechanism for reducing long-term energy intake. This research has culminated in piloting a limited variety prescription (variety of both HED snack foods and entrees at dinner were limited) within a 6-month family-based behavioral obesity treatment (FBT) for children. Twenty-four families, with a child > 85th percentile BMI and aged 8 to 12 years, were randomized to FBT that included the Traffic Light Diet (1000-1500 kcal/day, < 2 servings/day of RED [HED] foods) and a > 60 min/day of moderate- to vigorous-intensity physical activity prescription or to FBT that included a limited dietary variety prescription (one RED snack food and dinner entrée were chosen; families regularly consumed these foods as compared to other RED snack foods and entrees) (FBT+Variety). At 6-months children in FBT+Variety had a significantly greater reduction in percent overweight than those in FBT (-15.4% vs.- 8.9%), and families in FBT+Variety had a lower daily intake of kcal from fat (351 kcal vs. 494 kcal). This limited dietary variety prescription shows promise for enhancing weight outcomes in FBT. However, research is needed to examine if limiting variety improves long-term weight loss, if this improvement is due to enhanced habituation, and explore if there is a behavioral phenotype that more greatly benefits from this dietary approach.

The investigators plan to implement a novel limited RED food variety prescription within an 18-month FBT to examine its effect on 18-month body mass index (BMI). This will be the first RCT to examine how habituation rate, assessed via salivary habituation, mediates reduction in RED food intake, overall energy intake, and reductions in BMI over time, as well as if baseline habituation rate is a behavioral phenotype that moderates BMI outcomes. One hundred fifty-six children aged 8 to 12 years at > 85th percentile BMI will be randomized to one of two, 18-month interventions compared in our 6-month pilot study: FBT or FBT+Variety. Child and adult caregiver assessments will occur at 0, 6, 12, and 18 months on anthropometrics, dietary intake (RED food variety, energy, and diet quality), habituation, and physical activity. The investigation was designed for all intervention sessions and assessments to be conducted in person. Due to COVID-19, modifications have occurred to the trial for health safety reasons. Initially, all meetings and assessments were to occur in-person. Due to the constant changing health safety requirements due to COVID-19, the trial puts in place health safety practices to maintain the safety of participants. Assessment meetings and program meetings will occur remotely via Zoom.

The primary aims are to determine for children:

1. Influence of FBT+Variety on long-term weight loss.
2. Influence of FBT+Variety on long-term habituation to RED foods. The habituation rate will mediate differences in dietary intake and BMI between conditions.

An exploratory aim is to examine in children:

1) Influence of habituation rate on moderating outcomes in FBT+Variety and FBT (identifying a behavioral phenotype that bests benefits from a limited variety prescription).

Comparisons will also be made between the conditions on all child dietary and activity measures. Additionally, adult caregiver measures will be examined, with outcomes anticipated to be similar to child outcomes.

Inclusion Criteria:

• age between 8 and 12 years
• > 85th percentile BMI
• one adult caregiver (> 18 years) living in the household with a BMI > 25 kg/m2 willing to attend treatment meetings

Exclusion Criteria:

• child and adult caregiver report living in two separate households for > 2 days per week
• child or adult caregiver report a heart condition, chest pain during periods of activity or rest, or loss of consciousness on the Physical Activity Readiness Questionnaire (PAR-Q) (individuals reporting joint problems, prescription medication usage, or other medical conditions that could limit exercise will be required to obtain written physician consent to participate)
• child or adult caregiver report being unable to walk for 2 blocks (1/4 mile) without stopping
• child or adult caregiver report major psychiatric diseases or organic brain syndromes
• child or adult caregiver report currently participating in a weight loss program and/or taking weight loss or appetite regulation medication or lost > 5% of body weight during the past 6 months
• child report having bariatric surgery for weight loss/planning to have bariatric surgery in the next 18 months, adult caregiver having bariatric surgery in the previous two years or planning to have bariatric surgery in the next 18 months
• adult caregiver reports being pregnant, lactating, less than 6 months post-partum or plans to become pregnant in the next 18 months
• child or adult caregiver report planning to move outside of the metropolitan area (defined as from Nashville to the east state border of Tennessee) or Memphis (this may include residents who live in Arkansas or Mississippt) within the time frame of the investigation
• child or adult caregiver report dietary restrictions for medical reasons
• child or adult caregiver report allergies to lemon or lime juice (used in habituation measures)
• child is not able to read at a third-grade reading level.
• do not have reliable internet access.
• participation in the study creates conflict with child's educational support or health condition treatment/program due to time needs, incompatible goals, or strain on family resources.

Outcomes assessor will be blinded to randomization. Participants and providers will be blinded to study hypothesis.