When to eat

Main Meal  – Breakfast, Lunch or Dinner?

This article is an extract from Dr Jason Fung’s report on the same subject.

Physical and mental capacity is not impaired by a lion’s weeklong ‘fast’. They eat a large meal – storing much of the calories in their bodies and they are using these stored calories to survive. It’s normal.

Mammals have adaptations that allow them to survive with an intermittent food supply. That is, the body has a way of storing food energy so that mammals like lions can eat once a week. This goes for humans as well. The primary way to do this is to store glycogen in the liver (stored sugar) and then to store triglycerides in fat tissue.

When you eat, you are putting food energy into your stores. When you fast, you are pulling food energy out. It’s inconceivable that mammals were designed with this fantastic system for storing food energy and yet we find it necessary to eat every couple of hours to stay healthy.

Hunter-gatherer societies, as well as wild animals, virtually never got the problems of obesity, diabetes or cardiovascular disease, even during times of plenty. It is estimated that animal foods provided about 2/3 of their calories. So, for all the modern teeth-gnashing about meat and saturated fats, it seems that our ancestors had little problems eating them.

It should also be noted that many societies ate carbohydrate-based diets (e.g. Kitavans and Okinawans), and they also had no problems with obesity. It seems to be a modern problem, of refined grains and sugar playing an overwhelming role here.

So, it is certainly possible to eat meat and have little diabesity. It is also possible to eat carbohydrates and have little diabesity. The problem, (Nutritionist’s Greatest Blunder) is focusing obsessively on macronutrient content (how much fat, how much carbs). It’s the insulin response that matters, not the macronutrient breakdown. The toxicity lies in the processing, not the food. So highly refined and processed grains and sugars, as well as processed vegetable oils,  are the problem, not the carbs and fats.

Circadian Rhythms

Circadian rhythms are predictable, 24-hour self-sustained changes in behaviours, hormones, glandular activity etc. Most hormones of the body, including growth hormone, cortisol and parathyroid hormone are secreted in a circadian rhythm. These rhythms have evolved to respond to differences predominantly in ambient light determined by the season and time of day.

So, is there a difference between eating during the day and eating at night? One fascinating study compared the effect of eating a large breakfast versus a large dinner. While there are many association studies, this is one of the few intervention studies done in humans as opposed to mice.

What this study did was to randomly assign two groups of overweight women to eat a large breakfast (BF group) or a large dinner (D group). Both ate 1400 calories/day, and the macronutrient composition of each diet was identical – only the timing of the largest meal was changed. While both groups lost weight, the BF group was clearly superior for both weight loss and waist size (an important measure of visceral fat) by almost 2.5 times (8.7 kg vs -3.6 kg).

The BF group had more insulin in the morning while the D group had more at night, as expected. However, the dinner group had a much more significant rise in insulin. This is fascinating. The same total calories led to more insulin secretion simply based on meal timing.

Weight gain, of course, is driven by insulin. So, while the carbohydrates and calories were identical in both groups, the insulin response was not, translating into more weight for the D group. This illustrates the significant point that obesity is a hormonal, not a caloric imbalance. This study has profound implications over meal timing.

Now, this does not necessarily mean that you must eat a large meal as soon as you wake up. But it means that perhaps eating a large meal in the evening (after the sun goes down) may cause a much larger rise in insulin than eating that same meal during daylight hours. The problem with breakfast is generally that we are in a hurry in the morning and tend to eat very highly refined carbohydrates (toast, cereal, bagels, etc.) which also tends to stimulate insulin severely.

But waiting until noon to have a large lunch as your main meal seems to be a good solution. This also avoids the ‘rushing out the door’ or ‘grabbing a muffin’ sort of response to the exhortation to eat breakfast – it’s the most important meal of the day.

Ghrelin, the hunger hormone, shows a marked circadian rhythm with a low at 0800. Interestingly, with more extended fasting, ghrelin peaks at day 1-2 and then steadily falls. Many people on longer fasts report that hunger typically disappears after day 2.

Understand once again, that these are natural rhythms that are inherent in our genetic makeup. If you take away all external stimuli, these rhythms still persist. What does it mean that hunger is lowest in the morning? One implication is that hunger is not so simple as ‘the longer you don’t eat, the hungrier you’ll be’. No, there are many more subtle inputs and hormonal regulation of hunger playing a pivotal role.

So, what’s the practical implication? At 0800 in the morning, our hunger is actively suppressed by our circadian hormonal rhythm. It seems counter-productive to force oneself to eat breakfast.

So, the optimal strategy seems to be eating a large meal sometime between 12:00 and 3:00 pm and only a small amount in the evening hours. Interestingly, this is the typical traditional Mediterranean eating pattern. They have traditionally eaten a large lunch, followed by a siesta and then a small, almost snack-sized ‘dinner’. While we often think of the Mediterranean diet as healthy due to the foods, the timing of the meals plays a major role.

One final word of advice – We should DEFINITELY all take siestas.

Let’s eat our main veg and meat meal at 2 pm,

Michael Plumstead