Does Breakfast Really Matter?

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.

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5 thoughts on “Does Breakfast Really Matter?

  1. vinnygrette says:

    Yes, I think breakfast is important. But it doesn’t have to be huge. I’ve been eating one egg with all kinds of different veg for a year now and have lost 30 pounds. This morning I actually made a salad with arugula, heritage tomato, feta and my one egg on top. Yummy! Usually, though, it’s cooked – something like this:

    • vinnygrette says:

      I eat a fairly lo-carb diet, though – no sugar, few simple starches. Not sure entirely what the second para of your conclusions means 🙂

      • thanks for your comment vinnygrette!

        I follow a ketosis inducing diet, which essentially means that I eat under 30 grams of carbohydrates a day, which forces my body to burn ketones instead of glycogen for energy. Ketones are created from both digested fat and existing fat stores, and do not spike insulin. I try to stick to a 65/30/5% breakdown of fat/protein/carbohydrates when I eat, and find that it’s the most effective and pleasant way to achieve weight loss.

        Basically I’d like a study that more conclusively answers whether it matters when you eat calories, regardless of the nutritional make up of the meal. This study doesn’t quiet do that for me.

  2. Dave says:

    I am loving the fact that breakfast was proven to be the most important meal of the day! Let’s get people on the Epic Oatmeal bandwagon.

    Also, it was not lost on me that two out of three meals were served with a shot of espresso. Did you discover this study on your Caffeine-a-holics Anonymous site? 😛

    On a more skeptical note, the numbers in this study leave some room for doubt. First of all, the nutrition facts are ridiculous for normal portions. Where have you ever seen whole wheat bread that was 68 calories per slice? The wheat and multigrain bread I usually buy is 110-120 calories per slice. This entire diet would satisfy an anorexic and would positively terrify anyone else. Let us assume the average participant cheats somewhat and consumes 1500 calories per day for 12 weeks. Assuming participants maintained consciousness and did not fall into a coma or use a ride-on scooter for all travel, burning at least 2000 Kcal of energy per day should not be unreasonable. The 500 calorie deficit times 84 days works out to a 42,000 calorie loss during the course of the study. Assuming around 3,500 calories must be consumed to burn a pound of fat, this works out to a 12 pound weight loss, or 8%. So, the numbers do sound reasonable, should you be able to survive for a long period of time while starving yourself. If it were me, I would prefer to bump up the caloric intake by about 500 calories, while introducing some moderate daily physical activity to match.

    • Dave, keep in mind that the subjects of this study were obese, sedentary women. Many women aim for a calorie goal of around 1500 a day anyways. I do believe that 1400 a day is a bit extreme to jump into, but if they truly were sedentary (only moving to retrieve things from other rooms, go to the restroom, etc.) then that would be their “ideal” goal for normal weight anyways. I believe the espresso shots would be necessary for this approach to weight loss though, given that one of the requirements for being a participant was to not have been dieting previously (for several months before the study commenced) so they were probably eating 1000+ calories less a day than before.

      This study is far from perfect, but it is one of the better conducted nutritional studies available, unfortunately. When I find a better one I’ll make sure to post it and discuss 🙂

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