11 Factors that Affect Weight Loss (2023)

Have you always believed that weight loss should be easy, that it’s a simple formula of eat less and exercise more (i.e. burn more calories than you consume)? This is certainly what a lot of fitness and nutrition experts tell us.

However, the factors that affect weight loss are more complex.

If you’re in a cycle of dieting and exercise but you’re struggling to lose weight or to keep off any weight that you lose, it might be because other factors are affecting your weight loss too.

Let’s look at them in more detail.

  1. Genes

Why is it that some people can eat whatever they want without gaining weight, while others are destined to struggle with weight gain and, subsequently, trying to lose weight throughout their lives?

According to Harvard Health Publishing for Harvard Medical School, this comes down – at least in part – to our genes.

As the article explains, on a simple level our weight is determined by how many calories we consume, how many calories we store, and how many calories we burn. But these factors are heavily influenced by a combination of our genes and our environment, from the moment of conception onwards.

To date, scientists have identified more than 400 genes that have some influence over our weight. These genes affect things like our appetite, satiety (how long we feel full for), metabolism, food cravings, body-fat distribution, and even our emotional relationship with food, such as eating when we’re stressed or being predisposed towards eating disorders.

Current research suggests that there is a huge variation in how much our genes affect weight gain or weight loss. In some people, genes account for just 25% of the predisposition to be overweight or obese, while in other people genetic influence is believed to be around 70-80%.

How can you tell if your genes could be affecting your weight loss?

The only way you can determine for sure whether your genes are affecting your weight loss is to speak to a doctor who will be able to explore your individual case.

Broadly speaking though, you may be genetically prone to obesity if you fall into one of the following categories:

  • You have been overweight most of your life

  • One or both of your parents or other close blood relatives are significantly overweight (according to the Harvard article, if both parents are obese, there is an 80% chance, genetically, of the child being obese)

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  • You struggle to lose weight even when exercising regularly and following a strict low calories diet for several months

If you fall into one of these groups, your genes may only play a moderate role in affecting your weight loss:

  • Your weight is directly tied to and influenced by the availability of food

  • You can lose weight when you follow a moderate diet and exercise programme

  • You gain weight over holiday periods or during times of stress but can lose it again by adapting your activity levels and diet

If you rarely exercise and can eat high-calorie foods without gaining weight, then the chances are that you have a low genetic disposition towards obesity.

2. Race or ethnicity

There is a growing body of evidence that your ethnicity may affect your weight, both the extent to which you gain weight and how easy you find weight loss.

In America, stats from the National Center for Health Statistics show that obesity is highest among African Americans, then Hispanics/Latinos, and then Caucasians. Non-Hispanic Asians are least likely to be overweight but have been found to have higher risks of metabolic disease at a lower Body Mass Index (BMI).

Stats from The Centers for Disease Control and Prevention (CDC) in the US back this up but also highlight that there’s a complex interplay between ethnicity and socioeconomic factors that influence obesity, such as income levels, diet as you’re growing up, access to healthcare services or where you live.

More and more healthcare professionals are seeking to explore the degree to which your race or ethnicity can affect your weight and how this will impact effective weight loss support.

3. Age

Research shows that not only does our body fat increase steadily after the age of 30 but it moves more towards the centre of our bodies and our internal organs. Men most often gain weight until the age of 55 and women until the age of 65, after which many of us experience some weight loss, often due to a decrease in muscle mass.

Children who are obese may face a battle with their weight throughout their adult lives – as we’ve seen above, this may be because there is a significant genetic factor.

4. Sex/gender

According to NHS data, overall in the UK, 67% of men and 62% of women are classed as either overweight or obese. Being overweight (but not obese) is more common in men than women but being obese (including morbid obesity) is more common in women than men.

The same trend towards higher levels of obesity in women is reported in America too, rising even higher in African American women and Hispanic women. However, it’s important to recognise that women in these groups tend to face socioeconomic inequalities that may have an impact on their weight.

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5. Diet

There’s no doubt that both the quality and quantity of our diet affects our weight loss. If you eat and drink foods and beverages that are high in calories, sugar and fat, it may lead to weight gain.

This is where things can become complicated though.

Some experts believe that weight loss is a simple equation of fewer calories in than calories out (i.e. burned through activity). But does this mean that you could eat 1,000 calories of cake instead of 1,000 calories of vegetables and still experience the same weight loss?

After all, don’t all dietary calories have the same amount of energy (4,184 joules, to be precise)?

Yes, they do, but the human body is not that simple!

Different foods and macronutrients can affect our brains, our hormones, our appetite levels and so much more in very diverse ways. They go through different metabolic pathways, for example, which affect how much of the food’s energy is used and how much is dissipated as heat.

This is why it’s so important to make sure that, even if you’re following a calorie-controlled diet, it is as nutritionally beneficial as possible. One of the many reasons to follow a medically-led weight loss programme is to ensure that you’re eating the right foods to support your weight loss.

6. Physical activity/exercise

Physical activity and diet are often talked about hand-in-hand when people want to lose weight. The extent to which we’re active throughout the day – and the types of activities we do – have a direct impact on the amount of calories our bodies burn.

According to the CDC, increasing your physical activity is an important component of successful weight loss. However, it may be even more important for maintaining a healthy weight when you reach it.

Being physically active isn’t just about weight management though. Just 150 minutes of moderate-intensity aerobic activity per week (think a brisk walk, biking at a casual place, or playing with your children in the park) has been shown to:

  • Reduce high blood pressure

  • Reduce risk for type 2 diabetes, heart attack, stroke, and several forms of cancer

  • Reduce arthritis pain and associated disability

  • Reduce risk for osteoporosis and falls

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  • Reduce symptoms of depression and anxiety

Again, a medically-led weight loss programme tends to incorporate physical activity that’s designed around your individual goals, fitness levels and medical history.

7. Where you live and work

As we’ve touched on in a few of the points above, your weight loss may be affected by socioeconomic factors.

For example, do you have grocery stores and good fresh produce near where you live? Are you within walking distance of local green spaces or sports facilities? Do you have an expendable income for exercise classes or a gym membership, for example?

What are the catering facilities like at your workplace? Do you have to grab convenience food from a vending machine or is there a canteen offering nutritious meals? Are you able to bring food in from home? Do you often eat out with clients?

What kind of hours do you work? Do you get a proper lunchbreak? Perhaps you work shifts, so sometimes you sleep during the day and eat at night?

These factors and many, many more, will affect your overall health and wellbeing and, therefore, your weight.

8. Family habits and culture

Our commitment to losing weight and even how we perceive or respond to weight gain is inevitably influenced both by the families and friendship groups of which we’re part, as well as wider societal attitudes to body shape.

If you come from a family who eat a lot of high sugar foods or prefer sedentary activities such as watching TV or playing on a computer, you may lean towards the same habits in later life.

Similarly, if you are from a culture or religion that puts a lot of emphasis around certain food types or large family meals then this may influence your own experiences. Additionally, culture affects body image and body size perceptions from an early age. For example, in some cultures being overweight is seen as a sign of wealth, health, strength and fertility, while other cultures prize a smaller physique.

A report in Psychology Today showed how income affects eating and exercise habits. In the US and Europe, where thinness remains the beauty ‘ideal’, women in high-income brackets tend to be thinner than women in low-income brackets because they’re able to afford things like nutritional support, a personal trainer, gym membership, spa visits and even food being prepared and delivered to them according to a strict diet. They’re also likely to have friends and family members who adopt a similar lifestyle.

It’s worth noting that research published in the American Journal for Public Health found that food portion sizes have risen substantially since the 1970s and now exceed federal standards in America, directly contributing to the growing obesity epidemic. These trends have been seen in many other parts of the world, including in the UK.

9. Sleep

Good sleep may be an essential ingredient for effective weight loss.

Various studies have found that people who sleep approximately four hours a night experience negative changes to their metabolism as well as increased hunger and appetite, particularly for calorie-dense foods high in carbohydrates.

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One explanation might be that sleep duration affects hormones regulating hunger — ghrelin and leptin. Another contributing factor might be that lack of sleep leads to fatigue, which means you feel less inclined to be active.

Any steps you can take to improve your sleep are likely to benefit your overall wellbeing, as well as your weight loss goals.

10. Medical conditions and medication

There are many medical conditions that can cause weight gain or prevent weight loss. These include having an underactive thyroid, polycystic ovary syndrome (PCOS), depression, hormonal changes such as menopause, Cushing’s Disease, metabolic syndrome and others.

It’s also the case that medication for many different ailments can actually make it harder to lose weight. Medication for diabetes, depression, epilepsy, birth control or to lower blood pressure are just a few examples.

This is another reason why we champion medically-led weight loss here at Medikaur because it means you have a medical professional by your side to help you if you are on medication that’s affecting your weight.

There are also some medications that have been shown to support weight loss when used in conjunction with a healthy diet and lifestyle. Again, a medically-led weight loss programme may incorporate such medication, where approved for this type of use.

11. Stress

Last but not least, it’s worth thinking about how stress might be influencing your weight.

Evidence shows that ongoing stress in your life can cause your body to produce higher levels of the stress hormone cortisol.

Cortisol is the hormone that tells your body that it needs to get ready for ‘fight or flight’. Because it makes your brain believe that it will need spare energy to help you survive, it also cranks up your appetite to make sure that you get that energy.

If your cortisol levels only go up for a short while, you shouldn’t experience significant side effects but if you’re stressed all the time, your cortisol levels will remain elevated, causing the problems outlined above.

Other studies have found that your metabolism slows down when you’re stressed (probably to hang on to calories in case you need to make a run for it!) and that high cortisol levels cause us to deposit weight around our middles.

Taking steps to reduce your stress levels can have a positive impact on your weight loss too.


There is no one optimum weight definition, other than that we should all perhaps be aiming for the weight that is ‘best’ or most desirable for our physical frame and for our physical, emotional and mental wellbeing (again, defining optimum weight comes down to many factors!).

What’s clear is that the factors that affect weight loss and reaching our optimum weight are complex. It’s important that you consider all of them in your own weight loss or weight management journey.

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Find out more about the National Medical Weight Loss Programme at Medikaur here.


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