Losing weight is not easy, particularly if you’re doing this by drastically reducing how much you eat. If you've tried "all the diets" and still struggle to lose (or maintain) weight you may start to blame yourself, thinking that you just lack willpower or discipline. But - did you ever consider it's not you, but the diet? Or that there might be other factors at play?
An older study suggested that around 80% of people who achieve their desired weight loss tend to regain weight after 1 year, 85% regain weight after 2 years, and 95% after 3 years. In many cases more weight is regained than that which was lost. This suggests that it’s not an individual problem, that there are other factors that make weight loss challenging for many people.
We're not always in full control of our food choices: a number of factors play a role here, including your genes and food environment - especially the availability of highly palatable ultra-processed foods. It takes constant effort to maintain motivation, self-regulation and navigate tempting foods, social pressure, external influences and food-centered situations such as holidays.
Although rare, in some cases mutations of certain genes can promote weight gain, by producing a deficiency of leptin (the satiety hormone) or of a specific hormone receptor that impacts appetite and food choices (MC4R).
Your food environment describes all the different situations and settings where you have (or don't have) access to foods, and this plays a large role in influencing how likely you are to purchase, eat or drink certain foods and drinks, as well as how much you consume. Physical availability, marketing, product labelling, convenience, price, your income, your preferences and cooking skills also influence your choices.
Researchers that gathered feedback from people trying to lose weight found 4 main areas that make weight loss challenging:
navigating the food environment requires extensive planning to avoid less healthy options
easy availability of less healthy options consistently undermines weight loss efforts
higher price (real + perceived) of healthier options is challenging on a low income
social situations where food is involved, pressure from others to eat less healthy options, or negative comments about healthy eating efforts
Also - as you lose weight, your body adapts to lower energy (calorie) intake, which results in changes including slowing of metabolism, increased levels of ghrelin (hunger hormone) and reduced levels of leptin. Research has found that these hormones and resting metabolic rate can still remain at altered levels even a year after finishing a diet - which can make it incredibly difficult to maintain any weight lost.
Our obsession with calorie counting can also be unhelpful: when it comes to weight loss and dieting, calories are often the main focus (or sometimes the only focus). Calories are important to a degree when we’re looking to lose weight, but they're only part of the puzzle. There are a number of other factors that impact whether your body stores fat or uses it for energy including thyroid function, hormones (insulin, as well as thyroid, stress and sex hormones), your gut microbiota, sleep quality, stress, and nervous system function.
A food that is higher in calories isn't necessarily less healthy than a food that is lower in calories. Your body absorbs calories differently from different types of foods, so we can't accurately compare across foods. Around 97% of available calories are absorbed from fat as this is easier for your body to break down, while around 90-95% are absorbed from carbohydrates, depending on the type (your body will absorb more calories from sugar than from whole grains). The difference is even larger with protein, as we only absorb around 70% of these calories.
How much a food has been processed also affects absorption: highly processed foods are more available for your body to absorb, so you'll get more calories from these foods, while less processed foods are more intact and take more energy to digest.
Fibre also slows digestion of foods, and reduces the amount of calories absorbed during digestion, as fibre continues down to the gut to be fermented by your gut microbes.
So when it comes to weight loss, there are so many factors that play a role and diets that promote severe restriction of calories or food groups, or supplements and products claiming to produce rapid weight loss are most likely unsustainable fads and not helpful in the long term – and may even be harmful.
The best "diet" for you is one which you enjoy, can continue long term, and fits with your lifestyle, beliefs, and preferences.