Two diets with equal calories were compared. Eating a big breakfast did not result in greater fat loss or weight loss compared to a big dinner. There was no metabolic advantage of eating a big breakfast compared to a big dinner. Calorie utilization does not differ by time of day. Appetite scores tended to be lower for those eating a big breakfast than those eating a big dinner.
HUGE BREAKFAST VS BIG DINNER STUDY OF EQUAL CALORIES
Two diets with equal calories were compared. Eating a huge breakfast did not result in greater fat loss or weight loss compared to a big dinner.
There was no metabolic advantage of eating a big breakfast compared to a big dinner. Calorie utilization does not differ by time of day.
Appetite scores tended to be lower for those eating a big breakfast than those eating a big dinner.
The fitness community has been led to believe that magical “eating windows” can result in superior changes in body composition (i.e., greater fat loss and muscle gains). For many years, bodybuilders believed that nutrient timing or eating protein after workouts resulted in greater gains in muscle, yet we now know this is untrue. Similarly, consuming protein before bed was thought to result in greater muscularity, which was also proven untrue.
SHOULD A HUGE BREAKFAST BE THE BIGGEST MEAL OF THE DAY?
Current dietary recommendations are that a “calorie is a calorie” no matter what time you consume them. However, several studies have challenged this concept with findings that suggest that calories consumed earlier in the day result in greater weight loss than calories consumed later in the day. (Garaulet et al., 2013; Jakubowicz et al., 2013; Ruddick-Collins et al., 2018) Shift work can result in a circadian misalignment of our body’s natural rhythms, resulting in a risk of gaining weight and pre-disposal to diabetes.
The study by Jakubowicz et al. found that subjects consuming most of the calories earlier in the day resulted in greater weight loss than those consuming calories later in the day (i.e., 5.1 kg or 11.2 pounds more weight loss). Garaulet et al. found that a big breakfast with similar calories as a big dinner resulted in superior weight loss. (i.e., 2.2 kg or 1 pound greater weight loss). This suggests that calories in a big breakfast are less likely to be stored as body fat than similar calories in the evening.
SHOULD BREAKFAST BE YOUR BIGGEST MEAL?
Time-restricted feeding studies in which subjects must eat a big breakfast and skip lunch have also found greater weight loss results. The rationale for the advantages of more weight loss with a bigger breakfast has been contributed to greater thermogenesis, increased energy expenditure, and greater suppression of appetite-regulating hormones.
A CLOSER LOOK AT HUGE BREAKFAST-RELATED METABOLIC BENEFITS
We know the body has strict circadian rhythms regulated throughout the day. Chrononutrition is the science of how food, metabolism, meal timing, and your body clock interact. This section will break down some of the individual components and compare them to other research studies.
DOES A HUGE BREAKFAST INCREASE THERMOGENESIS?
A big breakfast has been suggested to result in greater calories burned compared to meals in the evening. (Morris et al., 2015; Richter et al., 2020) However, the work by Ruddick-Collins et al. has suggested that the higher circadian rhythms in the morning (i.e., glucose tolerance, lipid metabolism, gastric emptying, nutrient absorption, etc.) compared to the evening can explain the greater thermic effect of food.
The research found that when the body’s natural circadian rhythms are corrected, the thermic effect of food is similar for morning and evening meals. (Ruddick-Collins, Flanagan, et al., 2022) When natural circadian rhythms were not adjusted for, breakfast (60.8 calories) had a 2.4 greater thermic effect of food than dinner (i.e., 25.2 calories). They found that when they adjusted for circadian rhythms, there was no difference between breakfast (i.e., 54.1 calories) and dinner (49.1 calories).
DOES A HUGE BREAKFAST RESULT IN GREATER PHYSICAL ACTIVITY?
Early studies that found that a big breakfast is better for weight loss than a big dinner may be confounded by increased physical activity. An increase in physical activity accompanies most studies involving large meals.
The BATH BREAKFAST PROJECT found that a large breakfast (i.e., >700 calories) led to higher physical activity than eating a similar meal later in the day. Eating a big breakfast resulted in greater physical activity thru light movement than eating the same number of calories later in the day (i.e., 851 cals. in the morning vs. 442 cals. later)
NEW STUDY ON BIG BREAKFAST WEIGHT LOSS
A new study by Ruddick-Collins et al. published in Cell Metabolism performed a comprehensive study on all the factors mentioned earlier. Subjects had a 4-week diet in which they had all their calories placed in the morning, and then they completed a 4-week diet in which they received all their calories at night. Both groups had a 35% caloric deficit for each 4-week diet phase. The diet was 30% protein, 35% carbs, and 35% fat.
· The big breakfast group consumed 45% of their calories at breakfast, 35% of their calories for lunch, and 20% of their calories at dinner.
· The subjects then had their diet reversed and consumed all their calories at dinner. The subjects consumed a small breakfast, 20% of their calories at breakfast, 35% of their calories for lunch, and 45% of their calories at dinner.
This study provided them with all their foods and beverage,s so they knew exactly how many calories they consumed. The subjects had to track anything they drank and ate. The strength of this study is that the researchers provided all the meals for the subjects to eat. The researchers tracked body composition, energy expenditure, hormones related to appetite.,
HUGE BREAKFAST DOES NOT ACCELERATE FAT LOSS.
The researchers found similar weight and fat loss between the groups. The big breakfast group lost 3.33 kgs or 7.3 pounds, and the big dinner group lost 3.38 kgs or 7.4 pounds. There was no difference in % body fat loss, physical activity, or the thermic effect of food. (Ruddick-Collins, Morgan, et al., 2022)