The Meal Time Study
Condition: Obesity; Weight Loss
MeSH terms: Weight Loss
Study type: Interventional

Summary: 
      This weight loss study will investigate the impact of calorie distribution across a day
      (large breakfast meals and smaller evening meals versus small breakfast meals and large
      evening meals) on body weight, and physiological and behavioral mechanisms regulating energy
      balance.

      Participants will undergo 2 x 4 week energy restriction protocols in a randomized cross over
      design; big breakfast (45% of calories in the morning meal, 20% at dinner) and big dinner
      (45% of calories in the evening meal, 20% at breakfast). We predict that timing of eating
      will influence energy balance, because morning energy expenditure is amplified in comparison
      to the evening. This study will allow us to assess whether the increased energy expenditure
      in the morning is linked to natural biological circadian rhythm or behavioral adaptions.
    

Detailed description: 
      Dietary advice for weight management is broadly based on the assumption that a 'calorie is a
      calorie' and it does not matter when calories are consumed across the day. Recent evidence
      has challenged this assumption, suggesting that we may utilize calories more efficiently when
      consumed in the morning relative to the evening, and this could be used as a beneficial
      strategy for weight loss - this is a newly developing field of investigation which merges
      circadian biology with nutrition (chrono-nutrition).

      Timing of food consumption is a modifiable factor influencing energy balance and body weight
      (and thus, disease risk). Previous research has shown that calories ingested at different
      times of the day have different effects on energy utilization, leading to differential weight
      loss, even at iso-caloric amounts. This study will aim to increase our understanding of the
      underlying behavioral and physiological mechanisms associated with differential weight loss
      and energy balance when calories are consumed predominantly in the morning versus in the
      evening.

      This study will be a cross-over study comparing large breakfast versus large evening meals
      (percent daily calories split between breakfast, lunch and dinner as 45-35-20
      (breakfast-loaded) or 20-35-45 (evening-loaded)) during energy restriction (Fed to measured
      RMR) on energy balance, through differences in both physiological and behavioural changes in
      energy expenditure and substrate utilization.
    

Intervention name(s): Big Breakfast; Big Dinner
Intervention type(s): Other; Other
Intervention description(s): Weight loss diet (Calories fed to measured RMR) with calories distributed predominantly at breakfast (percent daily calories split between breakfast, lunch and dinner as 45-35-20%). The diet will be high protein (30% protein, 35% fat and 35% CHO) with all meals provided.; Weight loss diet (Calories fed to measured RMR) with calories distributed predominantly at dinner (percent daily calories split between breakfast, lunch and dinner as 20-35-45%). The diet will be high protein (30% protein, 35% fat and 35% CHO) with all meals provided.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: Weight loss; Chrono-nutrition; Diet; energy expenditure