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Have you ever felt insatiably hungry while dieting for weight loss, despite knowing you’ve eaten enough kilojoules to meet your body’s energy needs for the day? If so, you’ve experienced something of the interplay between hormones and weight gain.
A growing body of evidence is showing that we don’t have complete conscious control over our appetite and eating behaviours. If you sometimes feel like other forces within your body (such as hunger) are stronger than your willpower and sabotaging your best intentions, it could be these hormones at work. Knowing more about what these hormones do, and how they often undermine your attempts to lose weight, can help with your weight loss efforts.
The drive to find the fuel to generate the energy necessary for survival is wired into all living things. Hormones play a vital role in this process. Hormones are chemical messengers involved in controlling many body processes. They are produced by tissues in various parts of the body and circulate through your bloodstream.
Several hormones have an impact on weight. Sex hormones, growth hormone, and the hormones leptin, ghrelin and insulin all influence our appetite, metabolism and body fat distribution.
Hormone imbalance and weight gain have a two-way relationship: hormonal imbalance (excess or lack of hormones) can lead to obesity, and obesity can lead to hormonal changes.
Of particular interest in understanding how hormones influence weight are the hormones that affect your appetite and eating choices. They are produced in the gut (where food is digested) and the fat tissue (which stores energy as fat).
These hormones act as signalling mechanisms between your brain and body, and can subconsciously influence your eating behaviour and food choices. They are one factor in causing overweight and obesity.
When it comes to appetite, specific hormones are responsible for making you feel hungry (hunger hormones), while satiety hormones help you feel full.
The short answer is yes. The primary hormone known to make you feel hungry is ghrelin, the so-called ‘hunger hormone’. Discovered in 1999 by researchers in Japan, ghrelin is produced in the gut and is known to make you feel hungry. It also plays other vital roles in your body, with effects on muscle, blood pressure control, and mental processes, among others.
The exact relationship between ghrelin and obesity isn’t fully understood. However, research indicates that excessive ghrelin levels or heightened sensitivity to ghrelin’s activity may be involved. This could explain why you feel hungry even when you know you’ve eaten enough kilojoules to meet your daily energy requirements, which in turn can hamper your weight loss attempts.
Other hormones help you feel full (satiated), namely leptin, peptide YY, and glucagon-like-peptide-1.
Leptin is produced by fat cells and released into the bloodstream. It reduces your appetite by acting on parts of your brain that reduce your desire to eat. It also seems to regulate how the body manages its fat stores.
Because leptin is produced by fat, levels are typically higher in people who are obese than in people who are a normal weight. However, people who are obese can become less sensitive to leptin’s effects, and develop ‘leptin resistance’, with high leptin levels inhibiting your body’s ability to ‘burn fat’ for energy and lose weight. This also results in not feeling as full during and after meals and eating more than you need to. Consuming more food than you need leads to weight gain.
Produced in the gut, the hormone peptide YY also reduces appetite by acting on brain areas that control your eating behaviour. People whose bodies release low levels of PYY after eating don’t feel as full. Therefore, they may eat more than what they need to meet their body’s daily energy requirements, leading to weight gain. Evidence suggests that low PYY levels are linked with the development and maintenance of obesity.
The hormone glucagon-like peptide-1 (GLP-1) is released from the gut after eating. It helps to signal to your brain that you are full and that you can stop eating. GLP-1 also helps to slow emptying of food from the stomach, making you feel full for longer. Additionally, GLP-1 helps to control the release of the hormones insulin and glucagon (which are involved in glucose metabolism) from the pancreas after eating. Evidence suggests that the activity or effect of GLP-1 may be impaired in people who are obese. This may lead to faster stomach emptying and a delay in signals that you are full. In turn, this may cause you to eat more kilojoules than you need, resulting in weight gain.
The sex hormones, including oestrogen, also play key roles in appetite regulation, eating behaviour and energy metabolism. Oestrogen is produced by the ovaries in pre-menopausal women. It is also produced in body fat in small amounts in both men and women. Oestrogen inhibits food intake. This may help to explain why women tend to gain weight after menopause, when oestrogen levels drop. It could also explain why hormone replacement therapy with oestrogen helps counteract this weight gain.
Furthermore, the sex hormones affect body fat distribution. Women of childbearing age typically store fat on their lower bodies (hips, thighs and buttocks), while older men and postmenopausal women tend to store fat around their abdomen. Excess abdominal fat is linked with the development of numerous health conditions, including high blood pressure, heart disease, type 2 diabetes, fertility problems, osteoarthritis and some cancers.
People who are overweight or obese may have a hormone imbalance that encourages weight gain. Furthermore, over time, behaviours that contribute to weight gain may alter the internal processes that help to control your appetite and weight. This may create a vicious spiral that makes it increasingly difficult to lose weight and keep it off as your body fights to maintain energy balance.
Moreover, research shows that weight loss is associated with hormonal variations that encourage weight regain. Weight loss leads to persistent changes in hormone levels: levels of hunger hormones increase, while levels of satiety hormones decrease. This results in reduced feelings of fullness and a persistent increase in hunger. In turn, these changes oppose continued weight loss and hamper long-term weight maintenance efforts. Research suggests this is the case regardless of whether you lose weight slowly or rapidly.
It’s important to note that you cannot control your hormones through willpower. If you feel hungry, it’s extremely difficult to resist the urge to eat – regardless of how much you want to lose weight.
If you’ve tried losing weight by dieting or exercising before and found your body worked against you, your hormones may be part of the problem. The doctors at Rosemary Health are experienced at helping people lose weight, especially when lifestyle efforts alone haven’t been enough. Learn more about our doctor-guided weight loss program.