Weight loss supplements like Garcinia Cambogia may help a little, but successful weight loss depends on how much you eat and exercise and perhaps also the timing of your meals.
A recent study examined the relevance of meal timing among overweight or obese women on a weight loss program.
The researchers compared the effects of eating a large number of calories either at lunch or dinner on weight loss. Here is a detailed summary of their findings.
Growing evidence from controlled trials suggests that the timing of your meals may affect your health.
For example, eating most of your daily calories late in the afternoon or evening may adversely affect your blood sugar control(1, 2, 3).
Also, some studies show that eating a lot in the late afternoon or evening, relative to earlier in the day, may reduce calorie expenditure and promote weight gain (4, 5, 6).
These findings are supported by studies indicating that consuming more than half of your daily calorie intake at or before midday is associated with a lower risk of obesity, compared to eating that amount in the late afternoon or evening (7).
This study compared the effects of eating a high-calorie meal either at lunch or dinner on weight loss success among obese women.
This 3-month, randomized trial compared the effects of eating a high-calorie meal either at lunch or dinner on weight loss and heart disease risk factors in women.
A total of 80 overweight or obese women who were otherwise healthy participated in the study. 86% of them completed the study.
At the beginning of the study, all of the participants started a weight loss program that was designed to promote 7–10% loss of body weight over a 12-week period.
The program involved both diet and exercise and addressed potential difficulties on an individual basis.
The participants were advised to gradually increase physical activity levels up to 60 minutes of moderate activity five days a week.
Additionally, all participants were told to consume 15% of their daily calories at breakfast and 15% from snacks. Their calorie intake at lunch and dinner differed depending on which experimental group they were randomly assigned to:
- Main meal at lunch: 50% of daily calorie intake at lunch and 20% at dinner.
- Main meal at dinner: 50% of daily calorie intake at dinner and 20% at lunch.
To improve adherence to the diet, the participants had a meeting with a dietitian twice a week and recieved a phone call every weekday.
At the start and end of the study, the researchers measured the following:
- Body weight.
- Waist circumference.
- Calorie and macronutrient intakes.
- Fasting blood lipids – total cholesterol, HDL, LDL and triglycerides.
- Fasting blood sugar, insulin and glycated hemoglobin (HbA1c).
- Insulin resistance was calculated using homeostatic model assessment (HOMA).
Bottom Line: This was a randomized trial comparing the health and weight loss effects of eating a high-calorie meal either at lunch or dinner.
Finding 1: A Large Lunch Meal Caused More Weight Loss
The participants lost significant amounts of weight, on average.
However, having a large meal at noon promoted more weight loss (-12.9 lbs or -5.9 kg), compared to eating an equally large meal at dinner (-9.6 lbs or -4.4 kg), as shown in the chart below.
In contrast, there were no significant differences in waist circumference between groups.
Bottom Line: Eating a large meal at noon led to greater weight loss, compared to an equally large meal at dinner.
Finding 2: A Large Lunch Meal Improved Insulin Sensitivity
The weight loss program improved blood sugar control among all of the participants, but those who ate a large meal at lunch experienced slightly greater benefits.
Fasting insulin levels decreased by 2.01 mIU/mL among those who ate their largest daily meal at noon but only 0.72 mIU/mL among those whose main meal was dinner. Insulin resistance also improved in the lunch group, as shown below.
On the other hand, there were no significant differences in blood sugar or blood lipid levels between groups.
Bottom Line: Having a large meal at noon had greater benefits for blood sugar control, compared to eating an equally large dinner.
Why Does Eating a Large Meal Early in the Day Promote Weight Loss?
Controlled trials consistently show that eating most of your daily calories early in the day (at breakfast or lunch) may promote weight loss.
Scientists are not entirely sure how this happens, but they have come up with a few plausible theories:
- Increased fullness: A large early meal may lead to lower calorie intake throughout the day. The current study doesn’t support this hypothesis, as both groups appeared to be eating similar amounts of calories over the day (8).
- Reduced calorie expenditure: One study showed that an early meal caused a greater increase in metabolic rate and calorie expenditure than an identical meal eaten in the evening (4).
Further studies need to look into the possible physiological mechanisms. Since these effects are time dependent, they might have something to do with the body clock.
Bottom Line: It is incompletely understood why early meals may promote weight loss. Some studies suggest they may increase calorie expenditure.
The study was well designed and doesn’t appear to have had any major flaws. However, the authors pointed out a few limitations.
First, the intervention period was relatively short, or just three months. Longer trials are needed to find out if the effects are sustained in the longer term.
Second, the participants were overweight and obese women. Future studies should confirm these findings in other groups.
Summary and Real-Life Application
This study adds to a growing body of research suggesting that meal timing and daily calorie distribution may affect metabolism.
Specifically, the study showed that eating a large meal early in the day, such as at noon, improves the results of a weight loss program, compared to eating a large meal later in the day.
Eating the day’s main meal for lunch also reduced fasting insulin levels and insulin resistance.
If you are trying to lose weight and want to maximize your chances of success, eating your day’s largest meal for breakfast or lunch might be worth a shot