Cutting Carbs in Morning Equals Better Weight Loss, Waist Size

Becky McCall

October 09, 2018

BERLIN — Restricting carbohydrate in the morning, in addition to a low-calorie Mediterranean diet, led to improved weight and fat loss, lower body mass index (BMI), and a reduced waist circumference compared with the Mediterranean diet alone, shows a novel but small study from Greece.

Both diets had the same effect on glycemic outcomes in obese and overweight patients, a third of whom also had type 2 diabetes, but the so-called "morning carbohydrate restriction diet" produced slightly worse outcomes with regard to lipids compared with the Mediterranean diet alone.

Dimitrios Tsilingiris, MD, from National and Kapodistrian University of Athens, Greece, presented the findings here at the European Association for the Study of Diabetes (EASD) 2018 Annual Meeting

"The morning carbohydrate-restricted diet might offer certain benefits by favoring compliance...and the rapid weight lowering seen with this diet might be used in the induction of longer-term diets, or be an add-on feature in weight maintenance, even though it wasn't tested for this," he remarked.

It is known that carbohydrate-restricted diets achieve rapid weight and fat loss, as well as improve cardiovascular risk factors and hepatic steatosis in the short term.

"As such, they might be helpful in the management of obesity-related type 2 diabetes. However, these diets often have limited versatility and the availability of low-carbohydrate food can impair compliance. There have also been reports of long-term safety concerns with nutritional deficiencies and mortality," explained Tsilingiris.

He described the rationale underpinning the novel diet, which restricts the amount of carbohydrate consumed before lunchtime. "Normally, overnight we fast and in the morning, with breakfast, our insulin rises and then drops again towards lunchtime. As insulin drops, the fat stores tend to mobilize and act as energy substrates," he explained.

"Theoretically, inducing a lower insulin response after a low carbohydrate breakfast should mean we can prolong the low [overnight] insulin and fat mobilization state, resulting in a net effect on weight and fat loss."

Session moderator John Nolan, MD, from Trinity College, Dublin, Ireland, pointed out to Medscape Medical News that there is a good biological basis for this experimental diet.

"The approach to carbohydrate restriction around breakfast time is supported by the physiological argument that you would have less insulin and that might be the basis for the weight effects. Most people need more insulin at breakfast, so this is a distortion, but maybe it's a good one."

"It's a very practical diet, and if [these findings] can be reproduced, then there could be lots of clinical implications. It's exciting, and it's something to watch," he added.

Mean Calorie Intake for Both Diets Was 1300-1500 Kcal

The study aimed to compare the effect of an 8-week "morning carbohydrate-restricted diet" to a standard hypocaloric Mediterranean-type diet (control) on changes in body weight, body mass index (BMI), waist circumference, and body fat mass (somatometric parameters). Changes to glycemic markers (fasting plasma glucose and HbA1c) and insulin sensitivity (homeostatic model assessment — insulin resistance; HOMA-IR), as well as lipid profile, were also monitored.

In total, 70 patients (58.6% women) who were overweight or obese, around a third of whom also had diabetes, drawn from obesity and diabetes outpatient clinics in Athens were enrolled in the study. Participants were a mean age of 50 years and had a mean BMI of 34 kg/m2. Twenty-four had type 2 diabetes and had been on stable treatment for at least 3 months. 

After being allocated a daily caloric intake, each participant was randomized to one of the two diets:

  • For the morning carbohydrate-restricted diet, participants consumed between 300-500 kcal of very low carbohydrate foods (for example, eggs, hard cheese, ham, sausage) divided between breakfast and midmorning snack.

  • The Mediterranean diet (control) comprised 300 kcal of typical Mediterranean foods divided between breakfast and midmorning snack.

The two diets were identical for the rest of the day and comprised typical Mediterranean foods; remaining calorie intake was divided into lunch (45-55%), snack (10-20%), and dinner (30-40%). Participants were asked to keep a stable level of activity throughout the follow-up period. Mean calorie intake was between 1300 and 1500 kcal/day for both diets.

"From baseline to 8 weeks, both groups showed clinically meaningful improvements in somatometric parameters with statistical significance in both groups," reported Tsilingiris.

However, there were also differences.

"By study end, there was a mean 3.5 kg (7.7lb) greater weight loss for those on the morning carbohydrate-restricted diet versus the Mediterranean diet [P < .001]; and a difference of -1.05 kg/m2 [P < .001]; -3.21 cm2 [P < .001]; and -1.45 kg [P = .032] for BMI, waist circumference, and fat mass loss [respectively], all in favor of the morning carbohydrate-restricted diet," added Tsilingiris.

And more patients in the morning carbohydrate-restricted diet group lost 5-10% of total body weight than in the Mediterranean diet group, both by end of week 4 and 8 (at week 8: 77.1% vs 31.4%; P < .001). 

Everyone in the morning carbohydrate-restricted diet group achieved loss of baseline body weight of ≥ 5%by study end compared with 65.7% in the control group (P < .001).

Does Lack of Effect on Lipids Negate the Findings?

With respect to the other measures, including HbA1c, the results showed no significant differences between the two groups.

Finally, regarding the plasma lipid profile, high-density lipoprotein (good) cholesterol declined in both groups, from 1.28 to 1.21 mmol/L in the morning carbohydrate-restricted diet group and from 1.4 to 1.33 mmol/L in the Mediterranean diet group.

But triglycerides fell a little, and to a greater degree, among those on the traditional Mediterranean diet, from 1.51 to 1.19 mmol/L, than among those on the morning carbohydrate-restricted diet, from 1.33 to 1.16 mmol/L.

Following the talk, an audience member commented on the lack of any meaningful effect on lipids: "There is a modest beneficial effect on weight with the morning carbohydrate restriction, but the lipid results were less encouraging. So if we look overall, I'm unsure it is worth having a small effect in weight reduction versus a less beneficial effect on lipids."

Tsilingiris and Nolan have reported no relevant financial relationships.

European Association for the Study of Diabetes (EASD) 2018 Annual Meeting; October 4, 2018; Berlin, Germany. Abstract 193.

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