Weight Struggles: Why Can’t Some Lose, and Others Gain?

Everyone has their own weight goals – whether you’re trying to shed some pounds or put on some muscle, it can be frustrating when you’re not reaching them. But why does that happen? Why can some people eat virtually anything and not put on weight?

Unfortunately, we have not yet found a solution to this question. However, there are different factors that need to be considered when we’re trying to understand why some people can reach their weight goals easier compared to others. These factors can include their nutritional habits, behaviour, and even genetics.

How come you’re finding it hard to lose weight?

Perception – our greatest foe

Perception may be a key player in this conundrum. Most people may believe that they have control over their eating habits, so they don’t feel as threatened by potential outcomes like weight gain¹. They may think that they can easily solve that issue by changing their dietary habits.

An interesting pattern can be seen with weight perception and food choices in adolescents – studies have found that underestimating our weight may be a risk factor for obesity in some individuals, while overestimating weight might be associated with disordered eating². Unsurprisingly, those that perceive their weight to be normal have healthier eating patterns³. There has also been a connection between perceived health and exercise levels – those that see themselves as healthier are likelier to engage in healthy habits, like exercise⁴.

The importance of these studies lies in that our choices in our childhood and adolescence help us form habits that we take on with us during our lives. In fact, a long-term study has shown that adolescents that perceive themselves to be overweight had higher chances of becoming obese in a 12-year follow up period than adolescents who perceived themselves as healthy⁵. Therefore, our ability to accurately perceive our weight may play a role in our susceptibility to put on pounds.

And this may also play a role in our frustrations with those that can supposedly eat energy dense foods without gaining weight. We only see a part of those people’s day, and they may go home after an energy dense meal and choose less energy dense alternatives throughout the rest of their day. When measured, those that don’t seem to gain weight may not consume as many calories as you might think.

Activity – we burn most our calories from living

We all have different levels of activity, moving different amounts during the day. It’s likely that you already play sports or workout if you’re attempting to shed some weight, but structured exercise takes up only a limited amount of energy each day.

Non-exercise activity thermogenesis (NEAT) makes up the calories that are burned when we do activities other than exercise or sport. It can account for around 20% of our daily energy expenditure. People have different levels of activity, and so research suggests that for people of similar weight NEAT can vary by as much as 2000 kcal a day⁶!

Whether we’re likely to move more may come down to our genes, as regions of the genome have been associated with more daily activity⁷. They have even found certain genes which may be connected to the drive to exercise^8,9. However, we can’t blame everything on our genes, and having genetic susceptibility to be less active does not mean we can’t make a habit of increasing our daily activity.

Leptin – its role in keeping us full

When we eat, there’s a lot of hormonal crosstalk that happens between our gut and brain, helping us regulate our appetite and stopping us when we’re full. Some of us may be more sensitive to the crosstalk.

Our fat tissue sends signals to the brain to let it know how much energy the body has, and when we can use it as normal¹⁰. To do so, it uses leptin, a hormone which helps us know when we have had enough food¹¹. However, if leptin signals aren’t recognized by the brain perfectly, our brain may not recognize leptin¹². Leptin resistance, when this signalling fails, can contribute to obesity.

In the case of leptin signal failure, our brain thinks that it does not have enough energy, and so needs to regain fat – so it starts encouraging you to eat more and move less¹³. This might be why diets fail in promoting long-term weight loss. Therefore, loss of sensitivity to leptin can hinder weight loss¹⁴.

Sleep – a key player in the battle against weight

Sleep is important for overall health; however, we don’t always get enough sleep. Sleep deprivation affects the way we regulate our energy balance, as it can affect glucose metabolism and upregulate appetite. Partial sleep deprivation changes our appetite regulating hormones, like leptin and ghrelin, increasing our appetite¹⁹. You may also be less likely to be able to control cravings for junk food when you’re sleep deprived, increasing your chances of consuming foods you wouldn’t normally consume²⁰.

What if I can’t gain weight?

Struggling to grow muscle? Genetics can be important in how easy it can be to gain or lose weight. In fact, if you’re healthy thin, it might be a trait passed down from your parents – we’ve even found certain genes and genetic regions associated with it. Those that are thin usually have less variations known to increase a person’s likelihood of becoming overweight²¹.

However, not everything comes down to genetics.

You might be unable to gain weight because of similar reasons as those who can’t lose it – food, perception, and your activity levels.

You might not know the amount of energy your body requires daily. If you’re an active person, your basal metabolic rate may be higher than what you think it is. The basal metabolic rate is the amount of energy your body requires to function normally without accounting for daily activity like walking, fidgeting, or exercise²². Overweight people typically need a smaller number of calories than those of a healthy weight.

Add that to the calories you burn due to NEAT and sports or exercise you partake in to get an accurate picture of how much energy you need in a day. Remember – you need to be eating more calories than what you burn, so that you can gain instead of maintaining.

Are you sure you know how much you’re eating? Try keeping a food journal to keep track of what you eat – it will help you understand whether you’re really eating as many calories as you should be. Remember that foods like vegetables and soups are great but fill you up quickly without many calories. Choose foods like dried fruit, nuts, and dairy products for more energy in a portion. If you’re struggling with gaining weight, you might just be more sensitive to hormones like leptin, making you feel full even after eating very little.

However, this applies if you’re not suffering from a medical condition such as type 1 diabetes, thyroid disorders, polycystic ovary syndrome (PCOS) and you’re not on certain medication, as that may impact weight management²³.

So, while there’s no definitive answer to this question, there are many actions you can take to reach your weight goals.