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Humans are not designed for weight loss diets. It's in your biology.

Humans are not designed for weight loss diets. It's in your biology.

Is it time to break up with weight loss dieting?

Roughly 10% of us are on a weight loss diet at any given time. The average person may even try up to 126 fad diets across their lifetime. This is despite weight loss diets consistently being shown not to work long term for weight loss or health improvement.

Let's explore why weight loss diets do not usually lead to long-term weight loss what to do instead.


'Calories in, calories out' is flawed

The first problem is that weight loss diets usually “work” for short-term weight loss by cutting calories in some way. This is based on the aged concept of “calories in, calories out”- if we eat less calories than we burn, we will lose weight.

The thing is, the 'calories in, calories out' theory has been debunked for years. We are not robots and the amount of calories we burn is much more complex than this.

Our bodies have evolved complex mechanisms to maintain our energy balance because it is important to keep us alive. When we diet, the body interprets this as a famine and, in response, lowers its basal metabolic rate —the amount of energy we burn while resting. This survival mechanism saves energy during periods of food scarcity. 

As a result, dieters often find that their weight loss plateaus or even increases despite still following a low calorie diet.

The amount of calories we burn is impacted by:

  • The calories we are eating - if you eat less, your body will burn less calories
  • On-and-off dieting - if your body goes through famines (aka diets), it will burn less calories
  • Hormones - especially for people who are menstruating. Calorie needs (and hunger levels) can change significantly across the month
  • Movement - Daily movement and generally how active you are
  • Illness - we often need more when the immune system is hard at work, whether we know we are fighting infection or not
  • Temperature regulation - it takes energy to keep your body warm


The amount of calories we absorb or store in the body is impacted by:

  • Genetic differences in the way we metabolise food
  • Gut microbiome - influences the amount of calories you absorb from the food you eat
  • Stress levels - influences your digestion and fat stores
  • Sleep, mood and food beliefs- this can impact our digestion and appetite
  • Alcohol consumption - promotes fat storage in an effort to use up the alcohol calories 


Hormonal Changes

Weight loss dieting triggers hormonal changes that increase hunger, reduce satiety and increase fat storage. As such, dieting can lead to a stronger drive toward food and increased tendency to store calories in the body. Some key hormones involved include:

  • Cortisol: Produced in response to stress. In short periods cortisol is necessary to support everyday tasks. However, dieting has been shown to chronically raise cortisol which drives increased fat storage and impacts digestion.
  • Leptin: Produced by fat cells, leptin helps regulate energy balance by reducing hunger. Weight loss leads to decreased leptin levels, increasing appetite and reducing energy expenditure.
  • Ghrelin: Known as the "hunger hormone," ghrelin stimulates appetite. Dieting increases ghrelin levels, making individuals feel hungrier and more inclined to eat.

 Learn more about stress and hormonal influences in "Overcoming Emotional Eating"


Neurobiological Factors

The brain plays a critical role in regulating hunger, satiety, and food intake. The hypothalamus, a region of the brain, integrates signals from hormones like leptin and ghrelin to maintain energy homeostasis. Dieting can alter the activity of neural circuits, making high-calorie foods more appealing and increasing the reward value of eating.

This can make you more likely to use food to cope with stress or emotional triggers.


Psychological Factors

Dieting can lead to feelings of deprivation and an unhealthy relationship with food. We tend to crave the foods we are trying to avoid.

For a dieter this can be a combination of:

  1. physical hunger - which tends to drive us toward high calorie foods
  2. the “last supper” effect - If you believe a food is going to be off-limits, you are more likely to eat it in larger amounts.

Deprivation eating is often seen in the dieting-overeating cycle or when off-limits foods are present at social gatherings.

Eating off-limits foods often comes with feelings of guilt or shame and this can drive stressful emotional eating or trigger binge eating for dieters.


Our hormones can also be impacted by our beliefs about food.

When people drank identical milkshakes labelled with different calorie values, people who had - what they believed to be - the low calorie milkshake, reported feeling hungrier and also had higher levels of ghrelin (the hunger hormone) after drinking the milkshake. Those who believed they had a high calorie milkshake were reportedly more satiated and ghrelin levels were lower.

The milkshakes were exactly the same.

When people with Type 2 Diabetes drank identical drinks with deceptive nutrition labels, their blood sugar increases were more consistent with their beliefs about the sugar level than the actual sugar level itself.


Body diversity

We are not all meant to be thin.

Genetically, we have different body shapes and sizes that our body will naturally gravitate to. Scientifically called set point, it is regulated by complex interactions between the brain, hormones, and metabolism.

Trying to force the body into a lower weight will require unhealthy eating and lifestyle changes resulting in poorer physical and psychological health.

For many of us, healthy is at a higher weight. Our natural weight range can also change over time due to dieting, medications, trauma or chronic stress or just the natural ageing process, such as through the menopause.

If weight drops lower than your genetic set point, your body will want to increase your weight. To do this it will reduce metabolism, increase hunger and change how you store fat.

For many, dieting results in temporary weight loss, followed by a gradual return to your current set point.


What we can do instead of dieting

Weight loss diets lead to a fight with our bodies. In this process of fighting against our hunger cues and other self care needs, the body’s hunger cues will get louder and metabolism will get slower.

A more sustainable option to improve our energy and health is to work with the body through an approach called intuitive eating. Intuitive eating allows you to reconnect with your body as your number one guide to eating while drawing on nutrition and health knowledge that supports, but not overwhelms, you.

Intuitive eating allows your body to naturally get its food, self care and emotional needs met so it can gravitate to the weight and shape that best supports it.

With this approach, health related changes may involve:

  • Regular rather than erratic eating
  • Having nourishing food available through gentle planning and structure
  • Reducing alcohol consumption
  • Reducing or managing stress related to food, body image and other life stressors
  • Moving in a way that feels good - physically and mentally
  • Understanding your hunger and fullness
  • Appreciation for body diversity and improving body image
  • Engaging in positive social interactions and connection
  • Moving away from unrealistic societal ideals and finding what feels good for you.

Weight loss dieting is not healthy. Your body will gravitate to its healthiest place when we let go of control and focus on caring for our bodies.


Grab this free e-book for the first steps you need to stop stressing over food and start intuitive eating.


Hunger et al. 2020. An Evidence-Based Rationale for Adopting Weight-Inclusive Health Policy. DOI: 10.1111/sipr.12062
Tomiyaya et al. 2010. Low Calorie Dieting Increases Cortisol. DOI:10.1097/PSY.0b013e3181d9523c
Crum & Corbin. 2011. Mind Over Milkshakes: Mindsets, Not Just Nutrients, Determine Ghrelin Response. DOI: 10.1037/a0023467
Park et al. 2020. Glucose metabolism responds to perceived sugar intake more than actual sugar intake. DOI:10.1038/s41598-020-72501-w

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