High Caloric Intake at Breakfast vs. Dinner Differentially Influences Weight Loss of Overweight and Obese Women
Daniela Jakubowicz, Maayan Barnea, Julio Wainstein, Oren Froy
Who is this study about?
This study is one of the few that objectively measures the effect of caloric timing for females with metabolic syndrome.
A person who is suffering from at least three of these five symptoms can be said to have metabolic syndrome:
- Large Waist Size (for men: 40+ in., for women: 35+ in.)
- High Triglycerides (150 mg/dL unmedicated)
- Low HDL, or “good” cholesterol (for men: 40 mg/dL or less, for women: 50 mg/dL or less, unmedicated)
- High Blood Pressure (135/85 mm Hg or higher, unmedicated)
- High Fasting Glucose Level (100+ mg/dL)
The syndrome isn’t uncommon–as of 2010 over 34% of adult Americans have it.
This study’s aim was to show if there was any notable relationship between blood sugar and circadian rhythm, also known as your “brain clock”, which would affect weight loss.
What type of people were excluded from the study?
This study did not include participants who
- Had diabetes, or any abnormal internal organ function.
- Were pregnant or lactating.
- Were taking any type of medication that affects glucose, insulin, reproductive hormones.
- Were previously dieting
That doesn’t mean that the study cannot be applied to those types of individuals, but it should be kept in mind that, as with any dietary change, results may vary.
What did participants do?
93 Women (20-65 years old) with a BMI over 32.4 with metabolic syndrome were fed 1400 calories every day for 12 weeks. The group was split into two smaller groups:
- BF – This group received most of their calories at breakfast (700 calories), less at lunch (500 calories), and not much more than a snack at dinner (200 calories).
- DF – This group received a snack at breakfast (200 calories), a small meal at lunch (500 calories), and most of their calories at dinner (700 calories).
The women reported their meal intake from home with instructions to make note of everything they ate.
They were instructed to follow this meal plan, with some substitutions of similar nutritional value allowed:
Their hunger, or appetite scores, were assessed before and 30 minutes, one hour, two hours, and three hours after each meal by marking somewhere between 0 and 100 on a vertical scale.
A dietitian met with each woman twice a week.
Weight, blood pressure, and waist circumference were recorded every 2 weeks by the same person.
Shortcomings of the study
The women reported their meals from home. This is a pretty big problem to me, as it’s not uncommon for people to believe that “just a bite” isn’t worth recording. Also, participants were asked to adhere to a specific macro breakdown (fat, protein, carbohydrates), which is another challenge to record.
Participants were only withdrawn from the study if they exceeded their calorie goal (1540 calories or more) over 42% of the time, or over 3 days a week on average.
Activity levels were not recorded–participants were simply asked to stay at the same activity level they had been at beforehand, which was sedentary. They were only asked to note any change in activity level ever 2 weeks. I’m not sure if I agree with this, as “sedentary” can mean many things. Often times when calories are reduced, you move even less than normal–not fidgeting, needing more motivation to get up to grab a cup of coffee, etc. I would have been happier with this study if participants at least wore a pedometer.
Finally, what you’ve been waiting for!
The women who ate their biggest meal first (BF) ended the study with a 10% drop in body weight. The women who ate their biggest meal at dinner had a 5% drop.
The BF group also had a more significant drop in waist size, as well as their fasting glucose and insulin.
This study does suggest that breakfast is, in fact, the most important meal of the day, for those who eat the Standard American Diet, which is low fat, high carbohydrate, moderate protein.
What I’d love to see is another study that follows the same principle of eating calories early in the day, but with a ketosis-inducing macro nutrient breakdown.
After reading this study in its entirety, I’m not convinced that it’s the calories that affect weight loss as much as it is the timing of carbohydrate intake, or blood sugar spiking foods.