Carbohydrates Past 6PM Will Make You ... Lean! Eating All Carbs in the Evening Increases Body Fat Loss by 28% Compared to Standard Low-Calorie Diet.

Image 1: This are not the Israeli police
officers from the study. How do I know
that? They are not obese; the officers
in the study (Sofer. 2011) had BMI >30
(photo by Mark Probst)

While everyone in the health-and-fitness bloggosphere knows Martin Berkhan, from leangains.com, I suppose that only a few insiders will be familiar with "Kiefer's" Carb-Nite program. The counter-intuitive, or, should I say innovative (?) idea behind Carb Nite is to refrain from eating carbohydrates in the course of the day to then do a major carb-up in the evening. An interesting idea Kiefer, a fellow physicist, developed based on the observations that

1. against what you read on various health bulletin boards insulin resistance is naturally high early in the day and
2. high carbohydrate (re-)feeds or "carb back loading", as Kiefer calls it, have been found to reset a metabolic machinery that has been downregulated by previous fasting.

And while Kiefer asserts that this way of "fasting" won't get you to a stage-ready body fat percentage of <10%, the testimonials of his clients seem to prove that, after all, cyclical carb-fasting / carb-binging can reduce the metabolically most active fat depots at the midsection, which are thought to be the worst health offenders in the obesity pandemic.

The results of an Israeli study, which have recently been published in the prestigious Obesity journal (Sofer. 2011), appear to support the idea that a high carbohydrates intake in the evening cannot be as bad, as mainstream weightloss paradigms would have it. It were studies on the effects of Ramadan on the diurnal pattern of leptin secretion (i.e. how leptin levels change in the course of 24h) which sparked the scientists' interest in trying to modulate hormonal secretion patterns via "innovative dietary regimens" in ways that would decrease hunger and facilitate weight loss on a calorically restricted diet.

Did you know? Leptin, which is still purported as "the satiety hormone" is secreted in a diurnal pattern. In the average human being (who obviously eats >=3 carb-containing "meals" a day) serum leptin peaks at 1am, falls in the course of the day, reaches its nadir at 1pm and starts rising again at about 4pm. Serum levels of the adiponectin, a adipocyte hormone which plays a role in energy regulation as well as in lipid and carbohydrate metabolism, reduc[es] serum glucose and lipid levels, improves insulin sensitivity exhibitsand  an anti-inflammatory effects (Yildiz. 2004) and is generally regarded as possible "link between obesity, insulin resistance, and the metabolic syndrome" (Gil-Campos. 2004), on the other hand, follows a diurnal pattern
with zeniths at 11am and 1am and a general decline at night with a nadir at 4am.

Sigal Sofer and his colleagues hypothesized that they could shift the nucturnal peak of leptin levels to the day and thus decrease appetite and increase fatty acid oxidation during the day by mimicking the carbohydrate intake of a Ramadan diet, i.e. no carbs or rather no foods before sunset. And in fact, carbohydrate-fasting up to dinner turned out to be very beneficial for the 30 overweight police officers in the experimental group.

Figure 1: Changes [in %] of BMI, abdominal circumference and body fat vs. baseline [note: a -18% reduction of fat mass does not equal a -18% reduction of body fat] (data adapted from Sofer. 2011)

Compared to the control group, whose diets had the same macronutrient composition (20%
protein, 30–35% fat, 45–50% carbohydrates) and were calorically identical (1,300-1,500kcal) the subjects who ate all their carbs in the evening lost more weight and body fat and experienced a 19% greater reduction in waist circumference (cf. figure 1). Subjects in the high carb dinner group also reported a 13.7% higher rate in satiety at the end of the 180 day weight loss intervention, while the satiety scores of the control group decreased by -5.9% compared to baseline - and that despite a smaller drop in 12h leptin concentrations in the experimental group.

Figure 2: Changes of serum parameters in subjects following the "no-carb before dinner" vs. control diet after 90 and 180 days of dieting; values representing differences (experimental vs. control diet) in percental changes from baseline,e.g. -20% indicates that the respective value decreased by 20% more in the experimental group (data adapted from Sofer. 2011)

The beneficial effects on blood parameters were less pronounced than the anthropometric ones, but still significant (cf. figure 2) and, with the exception of a nonsignificant increase in triglycerides and total cholesterol, display a general trend towards greater improvements in the experimental group. And it is likely that the 44% increase in adiponectin in the experimental group (vs. 14% increase in control) is one of the causative factors of these improvements.

Figure 3: The meal composition of the experi-
mental diet (information adapted from Sofer. 2011)

In summary, a "simple carbohydrate manipulation" in the form of carb-fasting before dinner, improves hunger/satiety status, increases persistence in the weight loss process, and provides "better anthropometric outcomes, improved insulin sensitivity, improvement in metabolic syndrome parameters, less inflammation" compared to an identical low-calorie diet providing carbohydrates throughout the day in members of the Israeli Police with a baseline BMI level of >30. Whether the normal weight or even athletic part of the population can derive similar benefits from such an intervention does still have to be elucidated.