How Do Fat Burners Work?

Jessica Clifton

by Jessica Clifton

15th July 2020

Do you want to lose weight fast? That’s the promise a lot of fat burners make, but how do they work? (And perhaps the bigger question, do they actually work?) 

What are fat burners?

“Fat burner” is a non-technical term that refers to food or nutrition supplements that are intended to boost the rate of conversion of fat into energy. In principle, they increase the oxidation of fat, especially during cardiovascular, aerobic exercise. At the same time, they inhibit the absorption of fat.

How fat burners work

There are three ways in which fat burners claim to aid the burning of fat and, ultimately, help you lose weight. They:

  • Increase the rate of metabolism
  • Improve the oxidation of fats
  • Inhibit the absorption and storage of fats

The aim of fat burners is to increase your metabolic rate, helping you consume energy instead of storing it as fat. However, while this may sound like the Holy Grail of weight loss, it’s not a passive approach – you can’t simply wait for fat burners to do their magic, you still need to exercise, particularly aerobic or cardio types of exercise, such as running or swimming.

Proper exercise and caloric restriction are still the best options when it comes to weight loss, but if you want faster results, there are a lot of fat burners, such as diet pills and diet teas, which claim to have the answer. 

Do fat burners really work?

If you only listened to the companies who make the fat burners and their advocates, you’d believe that fat burners are the answer to weight loss prayers. However, there is no medical research to suggest that this is actually the case – medical research into weight loss shows, of course, that diet and exercise are the most effective ways to lose weight.

Diet and exercise are the two key factors in burning fat and losing weight

Diet and exercise are the two key factors in burning fat and losing weight

Fat burning food supplements are typically marketed as “natural” products, and this is true to a certain extent. Many or most of the ingredients in these supplements are indeed from naturally-occurring substances such as caffeine, which may aid in increasing the rate of metabolism.

However, this doesn’t mean that results can be achieved without any work involved. If you are currently overweight, fat burning supplements might help you burn fat faster when you exercise. Fat burners may also help reduce excessive appetite and boost energy – but you can’t just take fat burners and expect to lose weight. Exercise and a healthy diet are essential.

Food satiation is usually achieved if you have the right amount of glucose in the blood. Fat burners are said to help balance blood glucose by using fat molecules as the source of energy instead of the glucose from food. The result is food satiation. The aim is that by taking fat burners, you’ll feel less hungry, thereby reducing your food intake.

Fat burners work best in combination with the following:

  • Cardiovascular exercises – these are also known as aerobic exercises, which include jogging, swimming, jumping jacks, tennis, and basketball. Any type of exercise that involves rapid movement and is intended to increase the heartbeat can burn calories.
  • Low caloric intake – you can still eat anything you want but in smaller portions. Calculate the calories that you need each day and subtract around 10 or 20% from it.
  • Sufficient hydration – this does not necessarily mean that you should drink water all the time. It only means that if you feel thirsty, especially after an intense exercise, you should drink water to satiate your thirst.

Discipline and motivation are also key factors.

Are fat burners safe?

Food supplements that are approved by the Medicines and Healthcare Products Regulatory Agency (MHRA) are generally safe. However, some precautions should be taken. It’s important to carefully examine the ingredients in food supplements that are marketed as fat burners.

Food supplements usually contain natural ingredients that typically don’t have an adverse effect. There are some exceptions of course, and not all fat burners are created equal. People who have the following conditions should be careful in taking any food supplements and weight loss products without consulting their doctor:

  • Those with allergies
  • Those who take maintenance medicines
  • Pregnant women
  • The elderly
  • Those who are too young (teenagers and children)
  • Those who are not overweight

You should thoroughly research the fat burner(s) you plan to buy. Even products that already have approval from the MHRA should be carefully examined, and you should immediately notify your doctor of any adverse effects.

Do fat burners have side effects?

Even though fat burners are marketed as natural and safe, there are some side-effects to some people. Since most of these products contain stimulants like caffeine, they can cause disruption in your sleep pattern. This is especially true if you do not exercise regularly. Other side-effects include the following:

  • Anxiety and nervousness – some fat burners can elevate the level of the stress hormone cortisol, which can increase feelings of anxiety.
  • Elevated blood pressure – the stimulants in fat burners cause the heart to beat faster and may also cause the constriction of blood vessels. As a result, blood pressure may become elevated.
  • Behaviour changes – some people who take fat burners experience changes in their behaviour. These include irritability, nervousness, and aggressiveness.
  • Stomach upsets – some of the common digestive effects of fat burners include diarrhoea, constipation, and other problems with bowel movements.
  • Death – in a few extreme cases, taking fat burners causes fatality, especially amongst those with pre-existing medical conditions and allergies.

The science of weight loss

Weight loss can be attributed to several factors and mechanisms: lower caloric intake, a faster metabolism, inhibition of fat storage, muscle mass loss, and water loss. Losing muscle mass and losing water are both considered unhealthy, but losing excess fat is generally good – and that’s where fat burners promise to help.

As biological organisms, we use oxygen to “burn” energy in a slow but very efficient manner. In its most simple form, weight loss is just the reduction of energy-rich molecules, like fats, into water and carbon dioxide.

The process, however, is complex and involves several steps:

  • Step 1: Glycolysis – a glucose molecule is converted into two molecules of pyruvates
  • Step 2: Pyruvate decarboxylationpyruvate molecules are oxidised to acetyl-CoA and CO2
  • Step 3: Citric acid cycle or the Krebs cycle acetyl-CoA enters the cycle inside the mitochondria
  • Step 4: Oxidative phosphorylation – this establishes the proton gradient or chemiosmotic potential in the mitochondria
Cellular respiration is a set of metabolic reactions that take place in the cells of organisms to convert biochemical energy from nutrients

Cellular respiration is a set of metabolic reactions that take place in the cells of organisms to convert biochemical energy from nutrients

Weight loss chemicals

The biochemical reactions involved in burning fats are directly attributed to weight loss. These include hormones like insulin, leptin, and sex hormones.

Insulin stimulates the uptake of glucose from the blood in tissues such as muscles and the liver. If the blood sugar level is efficiently managed by insulin, the accumulation and storage of it as fat molecules are minimised.

Another important hormone related to weight loss is leptin. Leptin is produced by fat cells, which helps reduce your appetite. Its main role is to manage the storage of body fat.

Leptin is a hormone made by adipose cells that helps regulate appetite and control your metabolism

Leptin is a hormone made by adipose cells that helps regulate appetite and control your metabolism

Sex hormones like oestrogen and testosterone directly determine the distribution of body fat. There are clear differences in the distribution of body fats in men and women.

For instance, men tend to develop belly fat, otherwise known as “beer belly,” which is the accumulation of fat covering the intestines. Meanwhile, women are more prone to accumulate fats in their thighs and hips.

What chemicals can be found in fat burners?

Fat burner supplements contain various ingredients. Each ingredient or a combination of the ingredients has the additive effect of supposedly contributing to weight loss.

Some of the most common ingredients found in fat burners are the following:

  • Caffeine
  • L-carnitine
  • Green tea extract
  • Conjugated linoleic acid (CLA)
  • Forskolin
  • Chromium
  • Yohimbe
  • Glucomannon


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