Exercise Training and Time-restricted Feeding in Overweight and Obese Adults
Condition: Overweight and Obesity; Weight Loss
MeSH terms: Overweight; Weight Loss
Study type: Interventional

Summary: 
      Overweight and obesity prevalence in adolescents and adults continues to remain significantly
      high in the United States. While diet and exercise improve many consequences of obesity,
      dietary strategies are not always nutrient sufficient and manageable long-term. Thus, highly
      complaint dietary strategies that lead to fat loss, while maintaining muscle mass, are
      needed. Time-restricted feeding (TRF) may be an ideal dietary approach for reducing fat mass
      and cardiovascular disease risk, while diminishing the loss of muscle mass and strength
      associated with obesity and aging. TRF, unlike continuous energy restriction, does not
      require a restrictive energy intake10. TRF requires individuals to consume calories within a
      set window of time (example = 8 hours), inducing a fasting window of 16 hours per day. There
      are few human studies on TRF that measure their effects in combination with both aerobic and
      resistance training. One recent study found an 8-hour TRF program (16-hour fast) improved
      insulin sensitivity, decreased fat mass, and maintained muscle mass in resistance-trained
      males after 8 weeks. Thus, the feasibility of TRF as dietary approach should be investigated
      further.The aims of this study are to: 1) determine whether time-restricted feeding (TRF) is
      an effective dietary strategy for reducing fat mass while preserving fat-free mass with
      aerobic and resistance training; 2) evaluate potential changes in health-related biomarkers
      (cardiovascular profile and anabolic-catabolic hormones) and muscle health indicators (mass,
      strength and quality) after 8 weeks of concurrent training with TRF; and 3) examine the
      influence of caloric intake and macronutrient consumption on muscle health in the TRF and
      normal feeding (NF) groups pre- to post-concurrent resistance training.
    

Detailed description: 
      Overweight and obesity prevalence in adolescents and adults continues to remain significantly
      high in the United States in all socioeconomic categories, regardless of racial and ethnic
      backgrounds. This is important because aging is strongly linked with increases in adiposity
      and alterations to the distribution of fat in the body, including visceral, hepatic, and
      intermuscular fat stores. These areas of fat storage are independently associated with
      increased risk of cardiovascular disease (CVD) and physical dysfunction. These conditions
      represent a major health problem in the US and are often triggered by multilayered dietary
      imbalances and lack of physical activity.

      CVD is the leading cause of death in the United States, with 30% of adults older than 19
      years of age having hypertension, and 16.5% of all deaths being attributed to high blood
      pressure. Physical disfunction with aging, also referred to as sarcopenia and dynapenia, is
      the gradual and progressive loss of muscle mass, strength, and endurance. Sarcopenia is
      characterized by a 3-8% loss of muscle mass per decade after the age of 30 years, affecting
      30% of individuals over 60 years and 50% of individuals over 80 years. This age-related
      decline in muscle mass negatively affects strength, balance, and stability; leading to an
      increased risk of falls and impaired ability to perform activities of daily living such as
      walking, personal care, cooking, and chores. The most alarming consequence of decreased
      muscle strength is its ability to predict future mortality in middle-aged and older adults.
      While diet and exercise improve many health consequences of obesity and attenuate declines in
      muscle mass and strength, dietary strategies are not always nutrient sufficient and
      manageable for long-term use. Thus, highly compliant dietary strategies that facilitate fat
      loss while maintaining fat-free mass are needed.

      Continuous energy restriction (CER), a reduction in daily caloric intake up to 40%, is a
      primary dietary strategy to help individuals decrease fat mass and lower the risk of CVD.
      While CER can be effective, it is associated with poor compliance and appears to accelerate
      the return of pre-deprivation body mass levels once the restraints over feeding are removed.
      More importantly, CER is known for weight loss consisting of up to 10%-60% fat-free mass,
      which suggests a large proportion of metabolically active skeletal muscle tissue is lost
      instead of adipose tissue. TRF, a variant of intermittent fasting, is an increasingly popular
      dietary approach because it does not require a restrictive energy intake as with CER. TRF
      allows individuals to consume ad libitum energy intake within a set window of time (example =
      8 hours), inducing a fasting window of 16 hours per day. Literature from animal studies have
      demonstrated reductions in body weight, total cholesterol, and concentrations of
      triglycerides, glucose, insulin, as well as improvements in insulin sensitivity following
      TRF. Unfortunately, human studies on TRF are limited and few exist that measure their effects
      in combination with aerobic or resistance training.

      One recent study recruited 34 healthy, resistance-trained males and randomized them into
      either a TRF (16-hour fast) or NF group. The groups were tested before and after eight weeks
      of their diet assignment and standardized resistance training for body composition, maximal
      strength, and multiple health-related biomarkers. These biomarkers included total and free
      testosterone, IGF-1, blood glucose, insulin, adiponectin, leptin, triiodothyronine (T3),
      thyroid stimulating hormone, interleukin-6, interleukin-1B (IL-1B), tumor necrosis factor a
      (TNF-a), total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL),
      and triglycerides. After the eight weeks of training, the TRF group significantly decreased
      fat mass compared to a NF group (-16.4% vs -2.8%). Hormonal responses included significantly
      reduced levels of total testosterone and IGF-1 with TRF, typically seen during CER. Though
      these anabolic hormones were reduced, no reductions in fat-free mass and strength were
      observed. In fact, fat-free mass, as well as arm and thigh cross-sectional area, was
      maintained in both groups. Leg press one-repetition maximum increased significantly in both
      groups, and, while not significant, bench press one-repetition maximum increased in both
      groups. These increase in strength are important to note, considering the subjects were
      highly resistance trained. Another interesting effect of TRF was reduced blood glucose and
      insulin levels, which contributed to a significant improvement in HOMA-IR (insulin
      resistance). Adiponectin increased, while leptin decreased with TRF. These responses were
      said to be linked to an enhanced regulation of insulin sensitivity and an improved
      anti-inflammatory effect in the TRF group. Lastly, T3 and Triglycerides decreased
      significantly and TNF-a and IL-1B were lower in TRF compared to NF. Overall, the study
      established TRF as a beneficial dietary strategy to improve health-related biomarkers,
      decrease fat mass, and maintain fat-free mass. Therefore, the feasibility of TRF as a dietary
      approach, for improving body composition and attenuating the risk factors of CVD and physical
      dysfunction that occur with obesity and aging, should be investigated further.The study will
      recruit 40, overweight (determined by body mass index between 25.0-29.9 kg/m2) male and
      female participants (ages of 45-60 years old) who are not currently following a structured
      aerobic or resistance training program or dietary plan. This will be a randomized, controlled
      trial with assessments made pre- and post-intervention. All subjects will be scheduled for an
      8-week, standardized aerobic and resistance training program. Participants in TRF group will
      be required to consume all their energy intake in an 8-hour feeding window (12:00pm to
      8:00pm), and will perform their exercise training within that feeding window. Participants in
      the NF group will maintain their typical dietary habits. Once training is finished,
      participants will complete post-training assessments that include all pre-training assessment
      variables.
    

Intervention name(s): Time restricted feeding; Normal feeding
Intervention type(s): Other; Other
Intervention description(s): Time restricted feeding= consume food only from 12:00pm-8:00pm; Normal feeding= consume food per normal schedule
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment