PART 1 – Biology
It is often touted that weight loss is as simple as eating less and exercising more, and that with sufficient willpower all people can achieve this. Unfortunately, this is not the case. Weight is extremely complicated as it is influenced by a large number of interconnected factors, many beyond an individual’s control. As dietitians, we frequently witness frustration expressed by clients who have tried all sorts of diets with no success, and understand that a holistic weight-neutral approach to nutrition creates the best results. This can start by understanding the role that biology plays in determining a person’s weight.
Genetics play a major role in the size and shape of our body. It is estimated that 40-80% of weight is contributed to by genes, with over 300 single nucleotide polymorphisms (SNPs) associated with adiposity. These genes and SNPs influence our bone structure, musculature, metabolism and more. This means that if we had people following the same diet and exercise regimes, their bodies would all look extremely different.Set point theory refers to all people having a weight their body prefers to be at. When people sit above or below this point, their body will regulate intake and energy expenditure to return to this weight – in other words, via homeostasis. For example, weight loss at a rapid rate increases ghrelin secretion, increasing feelings of hunger to promote weight gain to an individual’s set point. Additionally, if we consume more energy than we require, our body will increase its temperature to increase the metabolic rate. A person’s set point is not fixed, however, and can be increased or decreased. If a person is seeking to lower their set point, we know that slow and sustained weight loss (0.5-1kg/week) allows the body to adapt to the reduced energy intake. This can’t be achieved by crash dieting or dramatically limiting calories, thus this is where an accredited dietitian can assist.
Hormones play an enormous role in appetite, metabolism and fat storage. We know that fat cells produce leptin, a hormone that signals satiety. Individuals with larger bodies produce higher levels of leptin however display resistance to its hunger-regulating mechanism. Rapid weight loss can decrease leptin production, thereby increasing appetite and causing weight gain. Gradual lifestyle changes prevent this rapid shift in hormone production, creating sustainable and effective changes in the long-term. Furthermore, sex hormones greatly impact body fat distribution. Changes to these hormone levels, such as during menopause, can greatly impact one’s body shape without changing their diet or exercise. Insulin is another hormone that greatly impacts one’s carbohydrate and fat metabolism.
Health conditions and medications
Numerous health conditions impact our weight and should be investigated prior to prescribing low-calorie diets. Hypothyroidism and Cushing’s syndrome impact hormone production associated with weight gain and obesity, which can’t be rectified with diet alone. Mental illness can also greatly impact an individual’s ability to maintain their healthiest weight.
There are a number of medications that may affect a person’s weight. For example, antipsychotics, antidepressants and corticosteroids are associated with weight gain. There are a number of reasons for this, such as by increasing lethargy, decreasing resting metabolic rate and fluid retention. It is beneficial to set goals surrounding cardiometabolic health for these individuals, as their weight may not be in their control whilst on certain medications. Again, an empathetic and weight-neutral approach can assist with increasing motivation to make positive dietary changes.
How a dietitian can help
At Healthfix, our dietitians assess all of these factors and more in the initial consultation. We see weight as complicated and stigmatised, and work with our clients on health goals greater than just the number on the scale. We work with, rather than against, a person’s biology.This article was written by Ashley Maiden and reviewed by Melissa Juergens (Healthfix’s Dietetics Department). Should you have any follow up questions regarding this information our dietitians will be more than happy to assist you.