Will fewer carbohydrates at breakfast help you lose weight?

A study just published in the journal Nutrition seems to show that in the context of eating fewer calories overall, eating fewer carbohydrates at breakfast may help you lose more weight (doi.org/10.1016/j.nut.2019.110578).

A team of researchers in Athens, Greece noted that people seem to have a fair amount of success at losing weight with a low-carbohydrate diet, although "long-term adherence to a strict low-carbohydrate dietary regiment may prove difficult for many people, leading to... weight regain."

There are several theories as to just why carbohydrate restriction works so well, with ideas ranging from people simply consuming fewer calories to carbohydrate restriction causing lower insulin levels and thus greater fat utilization ("fat burning"). There's some evidence for both - but the fact that people find the diet hard to stick to can not be ignored.

With this in mind, the authors designed a study that combines a traditional reduced-calorie diet with cutting carbohydrates only in the morning. Why a low-carb breakfast? The authors thought that extending the overnight carbohydrate fast into the morning hours might induce the body to continue burning fat through that same period.

They recruited 70 overweight and obese men and women to participate in their 2-month study. Working with dietitians, the authors calculated the appropriate number of calories each participant required to maintain their weight, then designed a weight loss diet individualized to that person that reduced their caloric intake by 700 calories (500 if that reduction resulted in a caloric intake under 1000 calories per day).

The participants followed a Mediterranean-style diet high in whole grains, legumes, vegetables and fruits, fish, and nuts, with moderate intake of dairy and low intake of red meats, saturated fats, and refined carbohydrates. Their diets were designed to provide an overall daily intake of 60% of calories from complex carbohydrates, 15% from protein, and 25% of calories from fat.

The participants were randomly assigned to one of two groups: a low-carb breakfast group and a typical breakfast group. The low-carb breakfast group were instructed to consume between 300 and 500 calories at breakfast, with no more than 2% of their daily carbohydrate allowance to be consumed at that meal. The typical breakfast group consumed about 300 calories of a typical Greek breakfast of whole grain breads or cereals, vegetables and fruits, milk or yogurt, etc.

The mid-day meal, afternoon snack, and evening meals were identical for both groups. Greeks customarily eat their largest meal in the middle of the day, so the lunch meal represented 45-55% of the participants' total daily caloric allowance, while the afternoon snack was about 10-20% of daily calories and the evening meal 30-40% of their daily calories.

Dietitians met with the participants weekly for the first month and every two weeks in the second month to help the participants stick with their assigned diets. At the start and end of the study the participants were weighed, their Body Mass Index calculated, their waist circumference measured, and blood tests were performed. Their body fat mass was measured with a consumer scale that measures body fat through bioelectrical impedence.

At the end of the study both groups had lost weight, reducing both their Body Mass Index and waist circumference, but those in the low-carb breakfast group lost, on average, about 3.5kg (about 7.5 pounds) more than those in the typical breakfast group, and lost about 3 more pounds of fat (again, on average).

Blood tests revealed that both groups reduced their HDL cholesterol (the "good" cholesterol), but those on the typical breakfast diet improved their LDL cholesterol scores (the "bad" cholesterol) more than those on the low-carb breakfast diet.

The authors state that "This study demonstrated that carbohydrate restriction in the morning hours enhances the weight loss effect of a hypocaloric Mediterranean diet in overweight and obese individuals."

What this means for you

Before you decide to never eat oatmeal or toast at breakfast ever again in favor of cheese and bacon, there are things to bear in mind with respect to this study. First, reducing your caloric intake by 700 calories per day is a pretty significant daily reduction in calories: a woman who usually would consume 1,800 calories per day would cut her caloric intake to 1,100 calories per day. That's just plain drastic - a more usual approach is to cut calories by no more than about 300-500 calories per day.

Would a less drastic reduction in calories have the same effect of significantly greater weight loss? This study was designed to maximize the amount of weight each group lost, thereby magnifying the short-term effect.

Finally, we want to remind you of a study we shared with you a couple of years ago, showing that those who consumed the majority of their calories earlier in the day lost more weight than those who consumed the majority of their calories in the evening. The participants in this study had their largest meal in the middle of the day - might that have had an effect?

If you decide to try this approach, remember that this is in the context of a reduced-calorie diet - simply switching from cereal or toast to cheese and sausage in the morning is unlikely to cause weight loss (not to mention the known health risks of processed meats).

First posted: February 5, 2020