Why diets don’t work: And what actually does for sustainable weight loss

Think diets are simply about helping you hit a healthy weight? Think again.

Unfortunately, dieting is a multi-billion-dollar industry that thrives on those of us who want to lose weight. In 2021, the global weight management market was valued at US$470 billion and is only expected to keep growing [1].

With such a profitable industry, it's no surprise that a new fad diet focused on losing weight is promoted to us every few months. Popular diets, from keto to intermittent fasting to juice cleanses, all promise to transform your body.

But the question is: do they actually work? Well, we've done all the research for you to answer the most important questions on losing weight, the reasons why diets don't work and what you can do to achieve long-term, sustainable weight loss.

What is a diet?

Does the word diet automatically make you flinch? If so, it's probably because the topic of dieting is loaded and complex. The simple definition of a diet refers to foods and drinks that are regularly provided or consumed [2].

But, in today's culture, a diet means so much more. Dieting is now associated with fad diets, which all promise fast weight loss and a quick-fix solution to a lifelong (and often genetic) problem [3].

Some of these diet programs eliminate foods and nutrients such as dietary fibre, carbs and vitamins that are important for your body and offer a stack of health benefits [4].

Most weight loss diets also aren't sustainable and can even lead to weight gain in the long term.

Four fad diets to watch out for

In the world of dieting, there are a few key programs that usually overpromise and underdeliver when it comes to weight loss.

So, we've rounded up four common diets that tend to do more harm than good.

The paleo diet

The paleo diet involves eating foods that our ancestors hunted and gathered, including meat, poultry, seafood, fruit and vegetables [5]. Basically, you can't eat processed food (which isn't fun or sustainable).

Although this may sound healthy in theory, human beings have certainly evolved since the era of hunting and gathering. The paleo diet cuts out valuable sources of food, including whole grains, legumes and dairy, which can be costly and restrictive.

The keto diet

The keto diet program has gained a lot of attention in the last few years, particularly through celebrity endorsements [6].

Keto revolves around eating a low-carb, moderate-protein and high-fat diet (around 75 per cent of fat compared to a normal 20 to 35 per cent). This achieves a state of metabolic adaptation, allowing your body to survive in a period of famine [7].

As with most fad diets, keto involves cutting out key food groups and is a restrictive diet that likely won't work for long-term weight loss. The keto diet can also cause low blood pressure, kidney stones, nutrient deficiencies and an increased risk of heart disease.

Juice cleanses

Juice cleanses are marketed as a detox for your body and are said to help you shed weight (particularly if you've 'overindulged' over the holidays). They claim to boost your metabolism and get rid of nasty toxins from your body [8]. But in reality, that is simply not true.

In fact, juice cleanses deprive your body of important and healthy nutrients, including fibre, which helps lower blood pressure and keeps you full after you eat [9].

Plus, your body does a great job of detoxifying itself thanks to your liver and kidneys (which naturally flush out toxins) [24].

Intermittent fasting

Intermittent fasting focuses on time-restricted eating, where you alternate between fasting periods and times when you limit your calorie intake.

It's based on the theory that fasting aids in decreasing appetite by slowing the body's metabolism. However, research studies comparing intermittent fasting with a traditional diet program showed both diet programs did lose weight, but had no significant differences [1o].

So, is intermittent fasting sustainable? Well, in the same research studies, there was a very high dropout rate, at 38 per cent, which reflects the real-life challenges of maintaining progress and sticking to this diet in the long term.

There is also a potential for increasing unhealthy eating habits and over-eating on days you don't fast (naturally, you'll be more hungry and want to eat more) because your appetite hormones are pushed into overdrive when you've consumed too few calories over previous days.

Why don't diets work?

Diets may appear to help you quickly shed some weight, but the long-term results won't really be what you want. So, why is the weight lost from diet temporary?

To start with, diets are incredibly restrictive. You have to focus on certain foods and stay clear of others, which in the long run is pretty difficult to do.

Labelling foods as 'bad' and 'good' and having 'cheat days' can make you 'overindulge' in higher-calorie foods. In turn, you start to feel guilty and feel like you've failed, and the cycle of overeating might continue.

This all can lead to some pretty concerning psychological implications. The National Eating Disorders Association reports that 35 per cent of 'normal dieters' will engage in pathological dieting, and of those people, 20 to 25 per cent will develop an eating disorder [11].

Another study conducted over a five-year period showed that dieting may lead to obesity and the development of eating disorders [12].

Why is dieting not good for weight loss?

We've all fallen victim to the diet industry at some point in our lives. After all, we live in a culture that celebrates thinness and makes us think we have to fit into a certain weight bracket to be perceived as desirable and healthy.

So it's no surprise that there are so many diets on the market that give us false hope and empty promises of weight loss. Often, dieting can be rebranded as wellness, marketing itself as clean eating under the disguise of health, wellbeing and empowerment [13].

In reality, whether it's pushed down on us through the diet industry or the wellness industry, diets just don't work, and the research confirms it.

Take these results from a 2020 meta-analysis that compared 14 popular diets, including the Atkins diet, Jenny Craig, Weight Watchers and the Mediterranean diet [14].

It's safe to say the results were far from favourable. Weight loss was achieved within six months, and blood pressure and cholesterol did improve. However, after 12 months, most of the weight was put back on.

And, there were also no significant differences in health benefits between all the different diets.

How media and diet culture keep the cycle spinning

Scroll through Instagram or flip through a glossy mag, and you’ll meet countless “before-and-after” shots, detox teas, and #bodygoals. This constant stream of idealised images does two things:

1. Sets unrealistic expectations. Airbrushed abs and week-long transformation claims make healthy, incremental progress look “too slow,” driving people toward extreme fixes.
2. Moralises food and bodies. Terms like “clean eating,” “cheat day,” and “summer shred” label foods (and people) as good or bad, feeding guilt, shame, and all-or-nothing thinking that fuels disordered eating patterns.

Recognising this influence and curating your feed for evidence-based voices can break the cycle and create space for healthier habits.

What are the long-term effects of dieting?

There are various long-term effects of dieting, all indicating they typically aren't good for you.

Diets cause your metabolism to slow down

To achieve long-term weight loss, you need to be in a calorie deficit (a.k.a. burning more calories than you consume through movement and exercise). However, diets can often encourage cutting more calories than you need, which in the short term may not affect you too much [15].

In the long term, this can completely change your metabolic rate, meaning the body stores everything you eat because you're in starvation mode [16].

Research suggests that you lose weight at slower rates when on a very low-calorie diet because your body overcompensates by slowing down your metabolism [17].

Long-term weight gain

Have you ever berated yourself for not keeping the weight off after a diet? Well, you're not alone.

A study found that 60 per cent of participants gained more than their starting weight in the three years after they stopped their diet [18].

Binge eating habits and emotional eating are also likely to emerge following a diet [19]. This is because you are depriving yourself of foods you enjoy eating (which are okay to eat in moderation).

Diets damage your relationship with food

Not only are diets physically unsustainable, but they are also emotionally harmful. Focusing on restrictive diets, counting calories and labelling food as 'bad' and 'good' causes a huge amount of stress and guilt.

Being stressed out when eating meals can lead to negative eating experiences and negative associations with food, ultimately leading to increased anxiety and depression.

Many eating disorders, including anorexia nervosa, bulimia and binge eating disorders (which can all result from a bad relationship with food), have high co-morbidities with depression and other mental health issues [20].

It can interfere with your hunger signals

Dieting messes with our body's natural hunger cues (our body telling us we need to eat or when we are full) [21].

Following a diet (like intermittent fasting) tells us when and how we are supposed to eat. But, what if we are hungry when our diet program tells us we shouldn't be eating? Instead of following our body's intuition, we listen to our diet.

This means we spend so much time suppressing our hunger, which, in the long run, makes it harder to regulate our weight, and we are less responsive to natural hunger cues.

What to do when diet and exercise don't work

So you've tried every diet under the sun, and nothing seems to help you keep the weight off. That's because diets are often unsustainable and won't help you achieve your long-term weight loss goals.

A healthy lifestyle is a lifelong commitment that looks different for everyone and comes with its share of ups and downs.

To achieve your long-term weight loss goals, you need to implement small and achievable changes to your lifestyle (SMART goals are a great way to do this) [22].

Simple ways to make sustainable lifestyle changes include:

• Eating a variety of foods from all five food groups [23]
• Eat regular meals (try not to skip breakfast)
• Drink plenty of water
• Don't ban your favourite foods — just eat them in moderation
• Mindful eating — listen to what your body is telling you
• Move your body — exercise can help burn excess calories and offers various health benefits. You don't have to go to the gym either. Instead, find a style of movement you enjoy, such as walking, Pilates or swimming.
• Cook your favourite meals from a restaurant at home. This way, you can control what you put in your food and still enjoy your favourite dishes.

Even with these smart lifestyle changes, you might still be struggling to shift those stubborn kilos. That's why we created our Weight Reset Program, offering a modern medical reset to your metabolic health.

Up to 80 per cent of your weight can be determined by your genes, so in many cases, diet and exercise alone are never going to cut it. Juniper's Weight Reset Program is designed and delivered by medical experts and health coaches and includes a breakthrough medication that works to decrease your appetite and regulate digestion.

The combination of health coaching, medication and one-on-one health tracking with your Juniper doctor will help you lose weight and keep it off in the long term.

Ready to get started? Find out if Juniper's Weight Reset Program is right for you.

Frequently asked questions

Still wondering why dieting never seems to work, no matter how disciplined you are? Below are some common questions people ask when they’re frustrated by fad diets, stalled progress, or mixed messaging in the wellness world.

Why do most diets fail?

Most diets fail because they’re based on restriction, not sustainability. They often cause short-term weight loss followed by long-term weight regain due to slowed metabolism, hunger hormone imbalances, and psychological stress.

Is it possible to lose weight without dieting?

Yes — sustainable weight loss often comes from building balanced, intuitive eating habits, moving your body regularly, and improving sleep and stress levels, rather than strict dieting. In some cases, medical support may be needed.

Do fad diets actually harm your health?

Fad diets can cause nutritional deficiencies, increase the risk of disordered eating, and damage your relationship with food. Extreme restriction can also lead to metabolic slowdown and hormonal disruption.

What should I do if diet and exercise don’t work?

If you’ve tried multiple diets and still struggle to lose weight, you may benefit from personalised support. Juniper’s Weight Reset Program, for example, combines medical treatment with health coaching for a holistic approach.

Why do diets make me feel worse mentally?

Diets often label food as ‘good’ or ‘bad’, creating guilt, shame, and anxiety. This black-and-white thinking can contribute to binge eating, low self-esteem, and even clinical eating disorders in some individuals.

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Image credit: Team Juniper