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The Science Behind Weight Management

Welcome back to the second instalment of my health & fitness themed blog posts. Last time, we looked at 3 popular diets that claimed to help people lose weight, despite their lack of scientific integrity. This week we're going to dissect some key aspects of our body that enable us to regulate our weight. When discussing body weight and health, it's so important to gain an understanding of how things generally work on the inside which will inform what choices we make on altering our health/weight. Even though there are many different components to this, I've chosen to look specifically at diet, hormonal control and the microbiome.

As I have now dedicated the next 4 years of my life to studying the tiny things (bacteria), I am by no means a scientific expert on human health but I do have 4 years of a biochemistry degree which really helped me go a bit deeper into the topics, so hopefully I can help make the information a bit more digestible in this post than trying to read a scientific paper (pun intended!).


For our body to work optimally, there are two types of nutrients that we need to ingest from our diet. They include macronutrients and micronutrients. Macronutrients are needed in large quantities and come in the form of carbohydrates, fat and protein. In contrast, micronutrients such as trace minerals and vitamins are required in much smaller quantities. Too little of these nutrients combined in the diet causes an individual to be malnourished. Even in a high calorie intake you could have very few nutrients included in the diet to be sufficient.

Fats contain 2x more energy than carbohydrates and proteins, but carbohydrates are easier to break down in the body. Proteins are not used to provide energy in the body as their role resides in the growth, repair and support of various bodily structures (muscle, connective tissue, hair, nails etc.). Carbohydrates are mainly found in fruits, wholewheat grains and vegetables as simple sugars and dietary fibres. Simple sugars are easily digestible whereas dietary fibres require the microbiome to help with the breakdown process. A lot of refined and processed carbohydrates usually contain more simple sugars than fibre which don't have as much nutritional content. This is why they're considered 'bad sugars', but in moderation, it doesn’t cause much harm at all.

Fats exist as saturated and unsaturated and the latter is often involved in important roles such as metabolism, delivering fat-soluble vitamins and insulating neurons in our central nervous system. Saturated fats can supplement the cholesterol content that we already make in our body which acts in hormone production and building cell membranes. High levels of cholesterol lead to cardiovascular issues as they can begin to deposit on tissue and block blood flow, thus the recommendation to have more unsaturated fats than saturated. Nonetheless, the right amount of saturated fats (which varies person to person) can be very beneficial to overall health. More information about macronutrients can be found here.

As with anything too much of one thing usually means you're lacking in another. It's important to consider that there is an unequal but balanced science to the make up of a 'healthy diet' which includes nutrients/foods from all groups.

Hormonal Control

The hormones that manage our weight and metabolism are part of a larger network called the endocrine system which includes the glands that produce and release hormones for their prescribed function. Weight gain/loss/management occurs primarily under the relationship between energy intake and energy output, thus activities that increase energy output may begin to alter our overall weight. There are a number of metabolic activities that are controlled by our autonomic nervous system (the one you don’t subconsciously control) that promote energy output, without the need for exercise, as it actually costs a lot of energy to perform these functions in our body. Your hunger hormones, ghrelin and leptin work side by side to give you a signal of when you need or don't need more energy. Ghrelin increases your appetite when you're hungry whilst leptin suppresses your appetite once you’re satiated.

The butterfly shaped gland at the front of your neck is known as the thyroid which produces thyroid hormones that mainly act to control your metabolism. This includes all forms of regulation such as your digestive system. Essentially, it controls your basal metabolic rate (BMR) which is how many calories your body burns just from performing unconscious metabolic activity. Overactive or underactive thyroids cause an imbalance to these actions which can be corrected with medication to restore stability.

Insulin is also another hormone produced by the pancreas which controls blood sugar levels. When you have eaten a meal rich of carbohydrates (i.e. easy access sugar), it's broken down to release small molecules of glucose which increase the glucose levels in your blood. Once you've used up what you need, insulin acts to reduce this high level of glucose in the blood by activating the conversion of glucose into glycogen which can be stored in your liver cells for future use. When this system doesn't work properly, individuals experience hypoglycaemia which is a high level of blood glucose levels that is not being converted into glycogen and the glucose can often leave the body in the urine taking a lot of water with it. This causes a huge imbalance of the body's nutrient composition which can be hugely detrimental to one's health.

All of these hormones work somewhat alongside each other in a huge complex and intricate system. However, these are huge parts of our weight management that we can't even control because it's our body's job to keep it all in check.

The Microbiome

The human gut is home to trillions of bacteria and fungi that are incredible little helpers. They help us with so many things including preventing us from getting sick and breaking down food that is too big for our body to do on its own. There's a particular group of bacteria called the Bacteroides which encode genes in their cells to make enzymes that break down big carbohydrates, so that we have energy to carry out all of our metabolic functions. The diversity of your gut microbiome comes from how it was passed down to you when you were born, your environment, genetics and what you eat. If a particular nutrient from your diet is missing, there's no need for a large population of bacteria to be there and so others win the competition of nutrient availability and dominate. Therefore, what we eat controls the type of bacteria we have in our system and how we break down food and therefore our whole weight management system too.

And there you have it, 3 areas of our weight management system that is dependent on our innate physiology. I hope this helped put some things into perspective (as it did for me when I was learning it). Remember that everyone is different and there is no one size fits all guide to gaining or losing weight, not to mention other chronic conditions that may interfere with the systems. Next time, I'll be wrapping up this theme by chatting about the good, the bad and the ugly parts of the health & fitness industry!

Make sure to subscribe as I'll be sending out some exclusive content next Friday on this theme. Join me on Instagram for more conversation & my January self care challenge!

Until next time,

D x

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