Circadian rhythms have powerful affects on metabolism and health. The best way to eat everyday is to have a large breakfast and lunch, while not eating dinner. This improves sleep and leads to better cell regeneration, which greatly benefits health. Only eating food within a limited time window is known as intermittent fasting. 

Amazingly, intermittent fasting regimens “induce the coordinated activation of signaling pathways that optimize physiological function, enhance performance, and slow aging and disease processes (1).” Other researchers note time-restricted eating has many health benefits (2) (3) (4). Circadian rhythms affect these benefits. The rhythms of nature influence the rhythms of the human body.

Circadian rhythms affect up to 20 percent of the human metabolome (5). Insulin sensitivity varies by time of day so much that there is a phenomenon known as afternoon diabetes (5). Many organs in the body operate on rhythmic cycles and function best at specific times in the day (6). Intermittent fasting synchronizes these rhythmic cycles, leading to better overall function and health.

Importantly, the best time window for eating is between 8am and 4pm. This is because circadian rhythms have such a powerful affect digestion and metabolic efficiency.

Time of day influences these processes because the body does not want to intake a lot of energy later in the day. This is because digestion disturbs sleep, which a time for autophagy to remove old mitochondria and cells. This is critical since old, inefficient mitochondria create more reactive oxygen species than new, healthy mitochondria. Researchers note removal of the most inefficient mitochondria helps protect cells from associated reactive oxygen species (7). If the rate of autophagy is too slow or too fast, then health problems can occur.

Food intake creates anabolic signals, which triggers the growth of new cells. The anabolic signals of food intake, such as mTOR, conflict with signals for autophagy, which are catabolic and designed to destroy rather than build. These catabolic signals are usually elevated during times of limited energy supply, such as fasting and exercise. Nature designs sleep as a time the body should fast and repair cell damage. 

Stopping food intake many hours before sleep lengthens this fasting period, strengthening the autophagic signal and increasing removal of inefficient mitochondria and cells.

In the long-term, increased autophagy will significantly reduce inflammation. A daily autophagic process is very important for improving health and is the primary reason intermittent fasting has so many health benefits.

In contrast, eating food throughout the day limits autophagy, which leads to more inefficient mitochondria and old cells in the body. As discussed, this inefficiency causes inflammation and multiple health problems.

In line with this concept, the body purposefully reduces glucose utilization later in the day to support autophagy. Research notes “there is good evidence to indicate that reduced glucose utilization, decreased insulin sensitivity, and inappropriately low insulin secretion are involved in causing decreased glucose tolerance in the later part of the day (8).” This limitation of glucose utilization redirects glucose for storage as fat on the body.

Therefore, eating more in the morning and not eating at night improves metabolism and limits fat accumulation. Unsurprisingly, research found eating more calories at breakfast rather than dinner has an association with lower fasting glucose and significant weight loss (9). Other researchers note how consuming most of the day’s food earlier linked to improved health and lower weight (10).

Meal frequency is also important. Research found eating two larger meals a day, one at breakfast and one at lunch, was better than eating six smaller meals a day for type 2 diabetic patients (11). Rather than eating multiple small meals throughout the day, eating two larger meals a day is a healthier way to eat.

However, because of limited eating time, meals need to be larger to meet nutritional and caloric requirements. This makes mealtime a more enjoyable experience. This style of eating increases both appreciation for food and strengthens appetite. The meals are also larger, allowing more servings and enjoyment. Also, less frequent meals free up more time to do other activities besides focusing on food.

A major benefit of intermittent fasting is weight loss. As discussed in Chapter 6, weight gain and obesity are often caused by metabolic inefficiency. By increasing the signal for autophagy, intermittent fasting helps to remove many inefficient mitochondria and old cells. This significantly improves metabolism and reduces inflammation, which benefits weight loss.

Some weight loss even occurs if the food itself does not change and the eating time window simply switches from night to morning. But, if nutrition quality and lifestyle habits are also improved, then there will be an amazing amount of weight loss and multiple other health benefits.

Intermittent fasting and eating with circadian rhythms also improves the many other health conditions chronic inflammation affects. Therefore, many people will benefit by applying this information to eating patterns.

However, beginning intermittent fasting may need to be gradual because the removal of inefficient mitochondria and damaged cells temporarily increases inflammation and reactive oxygen species. This healing process can be uncomfortable depending on current health. 

Importantly, the body depends more on fat metabolism during fasting. If someone has been on a low-fat diet for a while, then there initially may be too many variations in blood glucose levels to perform intermittent fasting. Many people on the standard modern high-carbohydrate diets are probably familiar with feeling terrible after not eating for a while. This is because the body has become too dependent on glucose and the insulin rollercoaster.

For this reason, improving overall nutrition by eating low-glycemic load foods and slowly increasing fat intake better prepares the body for intermittent fasting.

Pro tip: In addition to eating meals earlier in the day and avoiding food at night, a powerful way to synchronize circadian rhythms to Nature is to have a regular sunrise and sunset grounded meditation practice outdoors.