Everywhere you turn, there is a new diet or magic weight loss pill. Each promises to help you lose pounds, shed inches and slink into a smaller size. We’ve seen the grapefruit diet, the cabbage soup diet, the Hollywood diet, the Atkins plan, South Beach, Pritikin, The Biggest Loser, Weight Watchers, Jenny Craig and millions more.
One of the most enduring diet dilemmas, thanks to Dr. Atkins, has been the carbohydrate conundrum. First it was all carbs were bad, then it was simple carbs versus complex carbs. Let’s face it, we’ve been carbed to death.
But a new weight loss study may just turn all of the conventional “carb wisdom” on its head. According to Israeli researchers, the key to effective weight loss (not to mention a variety of other health markers), may lie in when you eat your carbs, rather than what you eat.
It’s a Hormone Thing
The researchers based their hypothesis on the knowledge that adipose fat, which is where your body stores calories, actually functions as an endocrine organ. Endocrine organs secrete hormones, and in the case of adipose fat, it secretes adipocytokines, which are hormones that control hunger, satiety, and play a role in insulin resistance and inflammation — all critical factors when you are talking about weight loss.
Another player is leptin, a hormone that is a kind of messenger from the adipose tissue to the brain, telling it if you are hungry or full. This is where the new study comes in.
You see, leptin secretion has been found to follow certain patterns. It is low from 8 a.m. until 4 p.m. It then begins to increase about 4 p.m., reaching its highest secretions around 1 a.m. The irony of this is that when leptin is at its highest level, and therefore most effective, most people are sleeping!
Similarly, there is another hormone called adiponectin that also plays a role in obesity, as it helps increase carbohydrate metabolism and reduce cholesterol, inflammation and blood sugar levels. Turns out, like leptin, adiponectin secretion is also lowest during the day. However, when a person loses weight, their adiponectin secretions increase during the day and decrease at night.
Given all this, researchers wondered if they could alter leptin and adiponectin levels by controlling when people ate carbs. Their theory was that by altering these secretions, people would enjoy greater weight loss, and possibly even improve insulin resistance, fat distribution, inflammation markers and cholesterol levels.
Creating a Meal Plan
Researchers recruited 78 police officers between the ages of 25 and 55, all of who had a body mass index (BMI) of greater than 30, which is considered obese.
Participants were randomly divided into two groups. For six months, both groups ate a diet that consisted of:
- 20 percent protein
- 30-35 percent fat
- 45-50 percent carbohydrates
- 1,300-1,500 calories a day
The difference was that the first group ate all of their carbs at dinner, while the second group ate their carbs throughout the day. Many of the carbs came from biscuits, potatoes, bread or rice.
Blood samples were taken from all participants at the beginning of the study, one week in, three months in, and at the end of six months. Additionally, hunger-satiety scales were given to each participant on those same days, every four hours before meals. Anyone who did not adhere to the diet or exceeded their calorie count was excluded from the study.
At the end of the study period, there were a total of 63 participants, 30 in the evening carb group and 33 in the carbs all day group.
It’s a Matter of When, Not What
At the end of the study period, researchers found that eating carbs only at night had a profound impact on the results.
While both groups had significant weight loss, BMI decreases, and abdominal and body fat reductions, these percentages were greater in the evening carb group.
On the hunger side, 67 percent of the evening carb participants had a decreased desire to eat, as compared to just a 19 percent decrease in the all day carb group. Similarly, no one in the evening carb group had an enhanced preoccupation with food, while 33 percent of the all day group had an increase in their preoccupation with food.
Glucose levels were no different. Those in the evening carb group saw a 20 percent decrease in fasting glucose at the end of the study period, while the all day group had a mere 8 percent decrease.
When it came to cholesterol, both groups enjoyed a reduction in triglycerides, as well as LDL cholesterol levels. But, when it came to HDL cholesterol (the good stuff), the evening carb group enjoyed a 41 percent increase at the end of the study period, as compared to a 26 percent increase in the all day group.
And, when it came to the inflammation marker C-reactive protein, the evening carb group had a 28 percent reduction, as compared to a 6 percent reduction in the all day group.
Finally, the big test — leptin and adiponectin levels. When it came to leptin, both groups saw a decrease in average 12-hour leptin concentrations, with slightly smaller reductions found in the evening carb group (21 percent versus 26 percent). Remember, less is best with leptin.
With adiponectin, the evening carb group saw significant increases in average 12-hour concentrations, with a 44 percent increase, as compared to a 14 percent increase in the all day carb group. And here, more is better.
So, to say it even more simply, saving carbs for dinnertime resulted in:
- More weight loss
- Lower BMI
- Reduced abdominal girth and fat loss
- Less hunger and preoccupation with food
- Decreased fasting glucose
- Reduction in triglycerides and LDL cholesterol
- Increase in HDL cholesterol
- Decrease in inflammation
- Reduction in leptin levels (hungry versus full hormone)
- Increase in adiponectin levels
Based on this, researchers concluded that “consuming carbohydrates mostly at dinner increases adiponectin levels, in comparison to the standard control diet, leading to improvements in insulin resistance, the metabolic syndrome profile, and inflammatory status.”
Not bad for a simple diet change!
Give It a Whirl
Rarely does such a simple diet change have such profound effects on your health, so why not give it a try. Keep your breakfast, lunch and midday snacks to protein- and vegetable-based options. And save the bread, potatoes or rice for dinner.
This could be one of the easiest and most effective ways to lose weight and improve your health that we’ve seen in a long time!
 Sofer, S. et al. Greater weight loss and hormonal changes after 6 months diet with carbohydrates eaten mostly at dinner. Obesity (Silver Spring). 2011 Apr 7. [Epub ahead of print].
 Ronti, T. et al. The endocrine function of adipose tissue: an update. Clin Endocrinol (Oxf). 2006;64:355-65.
 Coleman, R.A. and Herrmann, T.S. Nutritional regulation of leptin in humans. Diabetologia. 1999;42:639-46.
 Yildiz, B.O. et al. alterations in the dynamics of circulating ghrelin, adiponectin, and leptin in human obesity. Proc Natl Acad Sci USA. 2004;101:10434-9.
 Calvani, M. et al. Restoration of adiponectin pulsatility in severely obese subjects after weight loss. Diabetes. 2004;53:939-47.