Every competitor knows that eaten carbs at night is just about the worse thing you can do for weight loss, right? For years, health advocates recommended to eat your biggest carb meal early in the morning and then minimize carbs later in the day. There was some interesting research suggesting that carbs at night may actually lead to fat loss. It may be due to the leptin and insulin connection. Everyone has seen those pudgy rats that are leptin deficient or who don’t produce any leptin; these are otherwise known as “fat bastard” rats. Leptin is secreted from adipose tissue and basically tells the brain stop eating! Leptin “the satiety hormone” has been described as the “information provider” of adipose tissue status to receptors in the brain. It has been shown that leptin deficient have high caloric intake; people who don’t produce leptin have elevated increases in hunger and impaired satiety manifested as severe hunger, however when leptin deficient patients are given leptin, there hunger goes down 2. Reduced leptin that occurs with weight loss acts as a signal of nutritional deprivation, which may be the reason why when bodybuilders go on contest diets they are always hungry! Their body-fat starts dropping and their insulin levels are low throughout the day mostly due to eating less and exercising more. When leptin levels drop, the drop initiates an adaptive response to conserve energy, manifested by increased food intake, decreased energy expenditure and suppression of the reproductive (i.e. testosterone) and other endocrine axes 1. The drop in leptin levels from calorie restriction may also be a signal for reduced testosterone levels that occur when going on a diet. One of the stimulators of leptin levels in insulin, when insulin levels are increased acutely, there is increased energy expenditure, decreased food intake and basically a reversal of all the negative affects of low leptin levels. That why a cheat meal here and there can help the weight loss process by stimulating leptin secretion and keeping your metabolism going.
Insulin Stimulates Leptin Release
Several studies have reported a stimulatory effect of insulin on leptin synthesis and/or secretion in man. Insulin is considered to be a potent regulator of leptin, because plasma insulin concentrations decrease during fast and increase after re-feeding in parallel with plasma leptin levels6. Fasting plasma levels in men correlate with leptin levels; in insulin resistant men high insulin levels are associated with increased leptin levels10.
Its not glucose levels that increase leptin levels, but insulin levels as a previous report indicated that a single insulin injection increased leptin mRNA expression severalfold, independent of glucose concentration11. Several studies using isolated white adipocytes reported that insulin increased leptin secretion7, 8, 9. So when leptin levels start falling it signals a rise in appetite, that’s why rat’s that don’t produce leptin just want to eat all day. Previous studies have described a typical diurnal pattern of leptin secretion that falls during the day from 8 AM to 4 PM hours, reaching its lowest at 1 PM and increases from 4 PM with a peak at 1 am12, 13. Ironically, this crucial hormone responsible for satiety is at its highest levels when individuals are sleeping. Adiponectin is another hormone that plays a role in energy regulation as well as in lipid and carbohydrate metabolism, reducing serum glucose and lipids, improving insulin sensitivity and having an anti-inflammatory effect3. Researchers have previously been reported that you can alter the circadian rhythms of leptin by diet. For example, during Ramadan (fasting during the day and consuming an enriched carbohydrate dinner). These studies have demonstrated that the diurnal pattern of leptin secretion can be changed 4,5.
So having higher leptin levels during the day is going to keep you hunger better controlled, so the key is to maintain leptin levels while dieting, yet the role of when carbohydrates are consumed and leptin levels has not been studied yet.
On Low Calorie Diet, Eating Carbs at Night Enhances Fat Loss
Ok, so back to our study, the researchers from Israel thought that if leptin is high at night from leptin circadian rhythm which rise at night than eating a carbohydrate enriched meal while on a low calorie diet may cause a super spike in insulin that may cause a greater rise in leptin which may lead to reduced appetite throughout the day. The study group consisted of a seventy-eight overweight police officers (BMI >30) were randomly assigned to experimental (carbohydrates eaten mostly at dinner) or control weight loss diets for 6 months. On day 0, 7, 90, and 180 blood samples and hunger scores were collected every 4 hours. The experimental group was prescribed a standard low-calorie diet (20% protein, 30–35% fat, 45–50% carbohydrates, 1,300–1,500 kcal) providing carbohydrates mostly at dinner, whereas the control group received a standard low-calorie diet (20% protein, 30–35% fat, 45–50% carbohydrates, 1,300–1,500 kcal), providing carbohydrates throughout the day. The high carb at dinner group was basically kept on a low carb diet during the day and told to eat the most carbs at dinner.
The dinner consisted of either:
2–4 pieces of bread/4–8 pieces of reduced calorie bread + 1/2 cup of white cheese/1 slice of yellow cheese/ 2 tablespoons of humus/egg/1/2 a can of tuna fish/4 slices of pastrami + vegetable salad + 1 teaspoon of oil/ tablespoon of tehina/1/4 avocado/1 tablespoon of dressing + fruit/fruit yogurt/diet ice-cream/2 biscuits/1 cookie
1–2 cups of cooked rice/pasta/puree/corn/legumes/1–2 potato/1–2 sweet potato + 1 tablespoon of gravy + boiled vegetables/vegetables salad + 1 teaspoon of
oil/ tablespoon of tehina/1/4
avocado/1 tablespoon of
dressing + fruit yogurt/diet
ice-cream/2 biscuits/1 cookie
Both low calorie diet groups lost weight, but here is the shocking results: greater weight loss, abdominal circumference, and body fat mass reductions were observed in the experimental diet where carbs were eaten mostly at dinner in comparison to controls who ate carbs all day long14. Also to further shock people, significant improvements in glucose balance and insulin resistance, lipid profile (total cholesterol, LDL-cholesterol, HDL-cholesterol) and the inflammation markers (CRP, TNF-α, IL-6) were measured in the group that ate most of their carbs late at night! Also, subject’s appetite scores were lower when the subjects consumed most of their carbs later in the evening. The researchers speculated that the favorable increases in weight loss may have been due to the enhances leptin levels that occurred with the high carbs at night groups. Additionally, the carbs at night group had higher Adiponectin levels, which can explain the lower inflammation levels and improvements in insulin and glucose scores. Thus, dietary manipulation in which higher carbs at dinner will maintain higher daytime leptin concentrations during daylight hours in weight loss process may be beneficial.
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