One Meal a Day? Are human beings biologically programmed to thrive on only a single meal a day?

by Donnay Gallinetti (RD SA, UK)

What is the best diet for us human beings? How regularly and how much should we eat? This is an ongoing controversial debate. Carte Blanche had a feature in their programme on Sunday night (19th February 2017), posing the question: "are human beings biologically programmed to thrive on only a single meal a day?” Read on to see what we, as dietitians, say about this:

Myth # 1: It is healthy to eat only once a day?

Why this cannot be true: There are micronutrients essential to our health, which we all need on a daily basis. Eating only one meal per day, you would most certainly not be able to meet all of your vitamin and mineral requirements. For example, the recommended daily intake for calcium in an adult is 1000 - 1300mg per day, and if you had to meet these requirements in just one meal, you would have to drink 1 litre of milk with your meal. It would also be difficult to meet your recommended fibre intake if you were only eating one meal per day, which may lead to constipation, amongst other health issues.

Cognitive function may also be impaired, since your brain and central nervous system require certain nutrients and calories for optimal function. Without adequate nutrient intake, clarity and focus can be jeopardised, you may be slower to make decisions, and accomplish less work.

Although the cognitive function should not be impaired with mild low blood sugar levels, as the body will then compensate by producing glucose from fat cells in the body, you want to avoid having your levels drop below 3.8mmol/L as research shows severe impairment in cerebral glucose metabolism.  This is also the reason why insulin dependent diabetics should not try this way of eating as their bodies are not able to control glucose levels as well, and they run the risk of dangerously low blood sugar levels.

Myth # 2: Humans are designed to be carnivores

Thousands of years ago when we were hunter-gatherers, we may have needed a bit of meat in our diets in times of scarcity. Although we think we are, and we act as if we are, human beings are not natural carnivores. Sure, most of us are ‘behavioural omnivores’…that is, we eat and can digest and metabolise meat, and so that defines us as omnivorous. But our evolution and physiology are herbivorous.

Humans are capable of consuming and utilising both animal protein and plant matter. We are basically “opportunistic” feeders (survive by eating what is available), with more generalised anatomical and physiological traits, especially our dentition (teeth). All the available evidence indicates that the natural human diet is omnivorous and would include meat. We are not, however, required to consume animal protein. We have a choice.

With the exception of our canine teeth, our anatomy is mostly in line with herbivorous species. Our facial muscles are not developed to allow wide mouth gape, we tend to chew our food and will find it difficult to swallow whole (which carnivores do). Our saliva also contains digestive enzymes for the digestion of carbohydrates, which are lacking in carnivores. Our stomachs are much less acidic than those of carnivores who can break down protein very quickly. Lastly, our colons are longer and have a complex function of absorbing vitamins, minerals, salts and water, whereas carnivores have very short colons to control only salt and water levels.

Myth # 3: There is no need to eat breakfast

Breakfast is considered an important meal because it breaks the overnight fasting period, replenishes your supply of blood glucose and provides other essential nutrients to keep your energy levels up throughout the day. Eating breakfast sets a variety of biological processes associated with digesting and storing food into action, which result in increased energy expenditure known as diet induced thermogenesis. So, eating breakfast ‘kick starts’ your metabolism for the day. Research has also found that those who eat breakfast use more energy through physical activity (in particular during the morning) than those fasting. So it might be that skipping breakfast makes people feel less energetic, without consciously realising it, so they reduce their levels of physical activity. Skipping breakfast is associated with a heavier weight and increased fatness over time.

Myth # 4: Protein and fat does not elicit an insulin response

After you eat, your blood sugar levels increase and this triggers the release of insulin, an important hormone in managing how your body uses glucose. Different types of nutrients affect blood sugar differently, and maintaining an appropriate intake of carbohydrates, proteins and fats will help control blood sugar levels and prevent or manage metabolic diseases like Type 2 diabetes. Protein stimulates insulin release as much as carbohydrate does (because one of insulin's jobs is to send amino acids into lean tissues such as muscle), but protein doesn't supply rapid glucose like carbohydrate does. Fat doesn’t stimulate insulin at all.

So let’s look at the facts:

 We do not believe that following a diet based on animal products and animal fat is sustainable. Not for our planet anyway. We can sustain food supply and resources far longer if we all consume a combination of plant-based and animal products in moderation and according to our nutrient requirements.

We do not only eat for nourishment but we also eat for pleasure and it forms a very strong part of our social activities. If you only eat once a day, how will that impact your social life and interaction with friends and family? If you then do break the “rule”, how will that in turn affect your weight and health?

 It is also important to remember that one size does not fit all. What works for one person does not necessarily work for the next. We are complex creatures with various health and nutrient requirements in various stages of the life cycle. It is best to consult a registered dietitian to determine your unique requirements to meet your health and nutrition goals and to fit in with your lifestyle for long-term sustainability.

Please leave your comments and share your ideas! Until net time.