Research is currently inconclusive of timing of eating and the development of heart disease.
The bottom line is a calorie is a calorie and it does not matter when you take it. However, most people take most of their calories at night, in the US, dinner accounts for 34% of total calorie intake. Also working late and stress may lead us to indulge in high fat and high calorie snacks at night which may then add to the calorie intake. Most of the studies done are in animals, shift workers or people with late night eating syndrome, which is not representative of most normal people.
Research indicates that not following the natural rhythm of our bodies with regards to meal times may upset the metabolism of our body. Changes in circadian rhythm like staying in a dimly lit place led non-obese adults to feel hungrier at 8pm than 8am and a preference for sweet and salty food.
Hormones that support stress functions in our body like cortisol and adrenaline reach their nadir at 3pm and if we continue to strive to keep those levels up by drinking coffee in order to work late, then it may lead us to consume more sugar and fat.
Lastly, there is some research that the timing of eating may affect the levels of hormones which regulate appetite, ghrelin (increases appetite) and leptin (decreases appetite). Eating three main meals between 8am to 7pm led to ghrelin peaking earlier and leptin peaking later which reduced the amount of calories taken compared to eating between 12pm and 11pm.
Late night may result in metabolic changes which adversely affect heart health and lead to more diabetes.
In a study of 420 obese adults, those who ate their major meal after 3 pm compared to those who ate before 3pm lost less weight after 20 weeks, with exercise regimen and calorie intake being the same. They lost less weight and lost it slower.
In another study involving healthy women comparing those who ate lunch after 4.30pm versus after 1pm, women who ate later burned fewer calories and could not metabolise carbohydrates as well which led to a lower glucose tolerance which may then lead to an increase in diabetes. Everything else the women did was the same.
In a later study on people eating 3 main meals between 8am to 7pm versus 12pm to 11pm, people who ate later had more weight gain which lead to negative metabolic and hormonal changes.
Therefore late night eating can cause obesity which is a known cause for heart disease and glucose intolerance which leads to diabetes.
Foods to avoid eating late at night includes mainly all the snacks which have high sugar and fat content. Interestingly, a study of overweight and sedentary women who did exercise three times a week and took a 150 calorie protein shake at bedtime, led to reduced hunger in the morning and an improved insulin profile. The small protein snack helps to repair cells and muscle and there is increased metabolism from digesting the food. If we have to eat at night due to a let dinner, healthy food will help our heart health. Healthy food will include olive oil, fruits, nuts, legumes, fish, white meat and some wine.
To maintain good heart health, we should avoid emotional eating where the food consumed is mainly high in sugars and fats. We should also have regular proper meals to reduce the peaks and troughs of insulin leading to reduced feeling of hunger and the need to snack or eat more. We should stick to our estimated calorie requirements per day which can be referenced from the American dietary guidelines. We should also stick to a healthy diet and one such healthy diet recommended by the American Department of Agriculture and the American Heart Association is the Mediterranean Diet. We should avoid highly processed foods which have high salt, high trans fat and high sugar content.
Blood fat level is also known as triglyceride level and is usually reported as part of a blood cholesterol profile. The link between high triglyceride levels and cardiovascular disease is there but not that strong as it is not known whether it is independently associated with heart disease or a marker of heart disease. This is because high triglyceride levels are found in people who are obese, who have low HDL cholesterol levels and in pre-diabetic or diabetic patients.
The study that reported that late night eating and high blood fat levels was done in rats. Whether the data can be extrapolated to humans is questionable and a review by the British Heart Foundation in November 2017 had basically panned the findings.
High blood fat levels has been identified as a risk factor for cardiovascular disease. Population studies show that people with high triglyceride levels have a 4 fold increase in cardiovascular disease than those with normal triglyceride levels. High blood fat levels can lead to higher circulating small dense bad cholesterol (LDL cholesterol) and dysfunction of the blood vessel lining (endothelial cells) and macrophages leading to an increase in cholesterol plaque formation and buildup in the arteries. High fat levels can also induce inflammation of the blood vessels which can lead to an increased risk for heart attacks and stroke.
Dr Kenneth Ng
11 March 2018