In a previous article I discussed a study showing that skipping breakfast does indeed lead to greater food and calorie intake during lunch, but not nearly enough to compensate for the calories not consumed at breakfast.  The researchers were able to show this outcome because they allowed for ad libitum food intake at lunch, meaning that the study participants could eat as much food as they wanted. This makes perfect sense considering the entire point of these studies is to compare how breakfast consumption or omission affects subsequent food intake, but it leaves an incomplete picture of the metabolic and hormonal effects breakfast may or may not have.

What if eating as much food as you wanted at lunch wasn’t an option? What if you exercised later in the day? Many individuals who decide to skip breakfast do so in order to aid weight loss, and many may choose to monitor their food intake more closely and exercise. To help answer these questions and provide further insight into the effects of skipping breakfast, Clayton et al from Loughborough University, UK recruited eight healthy, young, recreationally active, habitual breakfast eating males to complete two experimental trials, breakfast consumption (BC) and omission (BO), in a randomized, counterbalanced order (meaning half did BC first and half did BO first) with food and calorie intake at lunch and dinner remaining constant.

At this point I do have to complain, yet again. I’m sure you can figure out why from the quote below.

During BC subjects were provided a standardised breakfast of 25% estimated daily energy requirements (DER), determined by multiplying resting metabolic rate (RMR) [16] by a physical activity level of 1.7. Breakfast consisted of crisped rice cereal, semi-skimmed milk, white bread, butter, strawberry jam and orange juice (Tesco, Cheshunt, UK). During BO, subjects ingested water (624 (44) mL) to match water contained in the breakfast of BC. Subjects were provided the same lunch and dinner on both trials. Lunch consisted of ham sandwiches, crisps and yoghurt (35% DER) and dinner consisted of pasta, tomato sauce, cheese and olive oil (40% DER). Subjects consumed each meal gradually over a 30 min period (Table 1).

At least this time the breakfast used butter instead of margarine. Anyway, I do have to give props to the researchers for being anal about water intake. Not only was it matched at breakfast, but also throughout the rest of the day so that it could not confound any subjective appetite ratings.

The experimental protocol was fairly simple and involved all participants remaining in a lab all day, thus mimicking what would be expected with a full-time desk job. After at least a 10-hour fast, the participants arrived at the lab at 8:00 am and ate (or didn’t) breakfast from 8:30-9:00 am, had lunch from 12:30-1:00 pm, and had dinner from 6:00-6:30 pm. A light-intensity steady-state cardio session was done from 4:00-5:00 pm, and various measurements were taken throughout.

The researchers found some anticipated differences between the groups around breakfast time, but for the most part everything was the same after lunch.

As could be expected from the thermic effect of food and carbohydrate-density of the breakfast meal, carbohydrate oxidation and energy expenditure were significantly greater from breakfast to lunch during BC, but were not different thereafter.

Respiratory exchange ratio (RER) during BC (■) and BO (□) (A); and Resting energy expenditure (B). On x-axis, white rectangle indicates breakfast, hatched rectangle indicates standard meal, black rectangle represents exercise. ^† Significantly different to BC (P<0.05); * Significantly different to baseline (P<0.05).

Hunger, desire to eat, and prospective food intake were all greater and fullness lower in BO compared to BC until lunch but not afterwards.

Subjective feelings of hunger (A), fullness (B), desire to eat (C) and prospective food consumption (D) (left panel) and AUC analysis (right panel) during BC (■) and BO (□). White rectangle indicates breakfast, hatched rectangles indicate standard meals, black rectangle represents exercise. ^† Significantly different to BC (P<0.05).

The concentrations of ghrelin and GLP-1, which can be viewed as “hunger” and “satiety” hormones, respectively, had minor differences between the BC and BO conditions only before lunch.

Blood glucose and insulin were not different at any time point.

Finally, heart rate during the exercise session was, on average, 4 beats per minute greater (134 vs 130) during BO than BC, but energy expenditure, carbohydrate and fat oxidation, and perceived exertion were comparable.

This study suggests that at least some of the effects (I say some because the researchers obviously can’t measure every aspect of human metabolism) of skipping breakfast are transient and disappear after eating lunch regardless of whether compensation for the missed meal occurs or not. However, lunch did provide a daunting 35% of daily energy requirements, which could have been more than enough to satisfy the participants in a single meal. Future research will need to determine if these effects persist when lunch in less energy-dense.

Regardless, it does appear that skipping breakfast can be an easy way to shave 25% of your caloric needs off your daily intake and not feel deprived, at least not after lunch. Importantly, fluid intake was held constant between conditions, and it may be that allowing for increased water, tea, coffee, or other zero-calorie beverages could make the fasting period much more bearable. Also, not everyone lies around all day doing nothing, so for those individuals who are active throughout the morning, skipping breakfast may lead to greater sensations of hunger.

Finally, it must of course be mentioned that the meals used in this study were pretty awful and translating the results to more Super Human eating patterns is difficult if not impossible. Nonetheless, we are left with yet another study that suggests a traditional breakfast is not the most important meal of the day.