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Why Diets Don’t Work – The Physical Impacts of Dieting

Feature, Food Relationship, Healthy Eating | September 19, 2019

Green vegetables, nuts and fruit smoothies spread across a kitchen table.
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There’s no doubt that we live in a world dominated by diet culture. No matter where you turn there is likely to be a conversation about body size, appearance, and the latest diet to “fix” all of the above.

But do diets ACTUALLY work? And more importantly – is the only way to pursue health by shrinking our bodies? Spoiler alert – the answer is NO to both.

I’m Marlee Coldwell, RD with Ignite Nutrition and the truth is, the majority of diets fail. Research shows that between 80-95% of those who participate in diets for weight loss actually regain the weight and often more. And it really has nothing to do with your strength or willpower. Diets are so difficult to maintain because they work against our physiology – our bodies are not designed to be starved & restricted. Think about it – If diets worked, would we always be chasing the next one?

With so many rules and restrictions, it’s no surprise that we yo-yo so much when dieting. The official term for this is weight cycling and it is harmful to our physical and mental health. That’s right – not only do diets not work, they can actually make our health WORSE in the long-term. A tough pill to swallow – I know – but today I want to review some of the evidence of both the physical and psychological effects that dieting has on our bodies and minds.

Physical Effects of Dieting

With weight cycling and recurrent diets, our bodies fluctuate a lot – not just in size and shape, but also internally as well. Our hormones, metabolism and day-to-day bodily functions actually shift when our weight fluctuates significantly, and not necessarily for the better.

With recurrent restriction, our bodies live in fear of starvation and undernourishment. In response, the body activates its “anti-starvation mechanisms” to regulate weight and prevent starvation. Researchers continue to study this topic to understand more about the weight cycling phenomenon and why it occurs. Although there is still lots to learn, there are some fundamental studies that show unfavourable physical health outcomes associated with yo-yo dieting. I’ve listed 5 of the major (and many) physical changes are linked to poor health outcomes in dieting:

Ready to ditch your diet and get healthy with the help of a registered dietitian at Ignite Nutrition in Calgary, Alberta? We can help!

Metabolic rate

There is a fine line between minor caloric deficit and starvation. It is very common for weight loss diets to promote very low energy intake – so low that you often eat below your basal metabolic rate (BMR), which is the amount of calories your organs need to function – it’s the amount of fuel you need even if you aren’t moving. You could be in a coma and still require this amount of energy to breathe, digest, and live.

When we consistently eat below our BMR, the human body starts to kick into emergency mode. Simply put, your body can’t tell the difference between a famine and a fad diet. It can only tell that it isn’t getting ENOUGH. As a result, the body kicks into overdrive, reserving as much fuel as it can for later. It tries to hold on to energy in our adipose (fat) tissue, leading to weight gain or stability, despite low caloric intake.

But that’s not all – the body also slows down it’s normal (and very important!) metabolic processes to preserve the limited energy you do have. So while we may see quick weight loss initially, the body sees this as dangerous and does everything it can to regulate and return to its predisposed natural ‘set-point’ weight, which can be defined as the weight that it feels it can function optimally at. 

Hunger Hormones

Cyclical dieting alters our hormones significantly. As a response to weight loss, our bodies try to regulate physiological functions by making up for restricted energy. In order to do this, your body signals to your brain to increase your hunger hormone (ghrelin), while simultaneously reducing your energy expenditure. The result? You desire more calories than you actually require, making it very easy to regain weight through excess consumption. In our practice, we often see restrictive eating lead to binge eating, a feeling of loss of control around food, and what people describe as food or carbohydrate ‘addiction’. This is NOT addiction! This is your body seeking fuel in the face of starvation – and the easiest way to undo it is to eat enough.

In addition to increasing ghrelin, yo-yo dieting also decreases the production of a hormone called leptin. Leptin is released from fat cells but is significantly lowered when we lose adipose tissue with weight loss. Lower leptin levels trigger a starvation response, causing your body to decrease its metabolic rate and use less energy in order to preserve fuel.

To sum up, weight cycling increases ghrelin and decreases leptin, resulting in stronger appetite, food fixation, lower energy needs, and feeling like a bottomless pit – like no amount of food would satisfy you if you gave yourself permission to eat.

Blood Pressure

Elevated blood pressure or hypertension is commonly associated with higher body weight, with many studies showing improved blood pressure with short-term weight loss. The problem with this hypothesis is that the research stops there. We don’t know whether the individuals in these studies gain the weight back or whether their blood pressure remains improved in the long-term.

Most importantly, was it the health behaviour that improved the blood pressure, or was it the weight loss? In a meta-analysis comparing studies with weight neutral versus weight loss approaches, there was NO significant difference in blood pressure reduction between the two, showing us that weight loss is likely not the reason why blood pressure was reduced, but rather the performance of health promoting behaviours.

When we look at weight cycling – which is a common side effect of dieting, one study showed that ‘overweight’ women who had repeatedly dieted had higher blood pressure than ‘overweight’ women who had never dieted at all – indicating that hypertension may actually be worsened by weight cycling and strengthening the evidence that prescribing diets come with inherent risk.

Blood glucose and insulin

Our blood sugars are regulated by a hormone called insulin. When we eat carbohydrates, they are broken down into glucose and absorbed into our blood stream, triggering a release of insulin. This is because glucose, our bodies preferred fuel, needs the help of insulin to move it from our blood to other areas of our bodies for use or storage.

For positive health outcomes, it is ideal to be insulin sensitive, meaning we require less insulin to bring our blood glucose levels back to normal. We know that requiring high levels of insulin can lead to poor health outcomes such as diabetes, inflammation, and strain on the organs.

When our weight fluctuates up and down, so does our insulin response. Studies do show that a decrease in weight may result in increased insulin sensitivity. However, we do know from statistics that weight loss isn’t maintainable. The challenge with this is that each time we lose and subsequently regain weight, our adipose (fat) cells also increase in size and number. With this increase in fat cells, we also see an increase in the amount of insulin circulating in our bodies. In short – more ups and downs with weight can actually result in more insulin production and resistance over time than if weight weren’t to have cycled! 

Cardiovascular health

This leads into the important topic of cardiovascular health. Because weight cycling is associated with storing more triglycerides and fat, there is the potential for this to build up in and around our organs and arteries, elevating the risk of heart disease and stroke.

One study showed that men who gained weight did not have elevated cardiovascular risk compared to men who maintained their “normal” weight. In the same study, men who gained weight and then rapidly lost weight did have elevated cardiovascular risk.4 This is just one example of how cyclical dieting can worsen cardiovascular outcomes. We need more research in this area to know the full impact yo-yo dieting can have on heart health.

To sum it up, many studies don’t look at the long-term outcomes – ie. what happens 2+ years down the line. Instead, they only outline the positives of immediate weight loss. This is hard to generalize to everyday life, because people usually DO put the weight back on. How can we assume that weight loss = long-term health? We can’t. We can assume that weight loss leads to short term improvement in metabolic markers but is not maintainable and subsequent weight gain is actually associated with a WORSENING of those conditions you were trying SO hard to improve! So, what should we do?

We can improve many biomarkers of health whether we lose weight or not. In a recent 2019 systematic review and meta-analysis, weight neutral approaches to health performed as well as weight loss approaches, without any of the risk (and a reduction in bulimia and eating disorder behaviour).

Instead of focusing on weight loss as the driver of change, we should instead be thinking about our health behaviours. Do we get enough sleep? How do we manage stress? Do we eat a balanced diet with a variety of foods? Are we non-smokers and non-drinkers? Do we have a positive relationship with food and our bodies? THIS is what matters in the pursuit of health, if we so choose to pursue it.

If you’re ready to end the diet cycle and pursue health from a weight neutral approach – our dietitians can help! Read more or book an appointment here.

Ready to ditch your diet and get healthy with the help of a registered dietitian at Ignite Nutrition in Calgary, Alberta? We can help!

References

  1. Melby, C.L., Paris, H.L., Foright, R.M., & Peth, J. (2017). Attenuating the biologic drive for weight regain following weight loss: must what goes down always go back up? Nutrients, 9, 468. Doi:10.3390/nu9050468

  2. Ochner et al. (2013). Biological mechanisms that promote weight regain following weight loss in obese humans. Physiol Behav. 0: 106-113. doi:10.1016/j.physbeh.2013.07.009.

  3. Bacon, L. & Aphramor, L. (2011). Weight science: evaluating the evidence for a paradigm shift. Nutrition Journal, 10:9, http://www.nutritionj.com/content/10/1/9

  4. Stevens et al. (2012). Long and short-term weight change and incident coronary heart disease and ischemic stroke. American Journal of Epidemiology, 178(2): 239-248.

  5. Dugmore, J. A., Winten, C. G., Niven, H. E., & Bauer, J. (2019). Effects of weight-neutral approaches compared with traditional weight-loss approaches on behavioral, physical, and psychological health outcomes: a systematic review and meta-analysis. Nutrition Reviews.