Why Diets Fail and How to Eat Healthier

New Years is in the rearview mirror, and so are most of our resolutions...

Bill Tancer
— Signos
Chief of Data Science
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Reviewed by

Bill Tancer
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Science-based and reviewed

April 23, 2024
August 10, 2021
— Updated:
March 1, 2024

Table of Contents

Research has shown that many people — more than a third of the population — admit to altering their eating patterns, with more than 40% of those people citing weight loss as the primary motivator behind their food choices.1 Yet, somehow, the success rate for crash diets is very low. A recent systemic review analyzed the data from 121 weight loss trials and found that most dieters lost weight and saw improvements in their blood pressure levels within six months. However, those health benefits largely disappeared within 12 months.2

So, why do diets fail?

Restrictive diet plans can often lead to short-term weight loss, but because they’re not usually sustainable long-term, you can experience fluctuations on the scale. This yo-yo weight management can be exhausting, both mentally and physically. Thankfully, there’s a better way to embrace overall wellness and make the most of your food intake.


Why Diets Fail? 5 Reasons

Implementing dietary changes looks different for everyone because no two bodies are the same. Diets may be unsuccessful for a variety of reasons, including:

1. You’re Relying on Willpower Alone

When we often set out to lose weight, we frequently go all in and hope for that instant gratification to keep us motivated. Unfortunately, life is unpredictable, and motivation can be wavering. Relying on willpower alone to power through severe dietary restrictions isn’t practical. Instead, focus on lifestyle changes that are realistic for you, and remember that sustainable weight loss takes time.

2. You’re Not Eating Enough Calories

Many fad diets provide individuals with blanket recommendations, usually focused on restricting calorie intake. Some recommend low-carb plans, while others recommend low-fat. Unfortunately, and thankfully, nutrition doesn’t work like that. Nutrition is not one-size-fits-all — it’s very individualized. You know your body’s needs better than anyone else could, and it’s essential that you honor them.

The human body actively tries to maintain its existing weight, so nutritional changes for weight loss have to focus on more than just calories in and out.3 It requires a multifaceted approach that goes far beyond calorie counting; it requires a balance of carbohydrates, protein, fat, and micronutrients. Otherwise, you may experience weight gain as you incorporate more calories into your routine.

3. You’re Not Eating Enough Fat

After years of focusing on low-fat diets to combat obesity in the diet industry, many Americans are left confused about the role that dietary fat plays in the body. The body relies on dietary fat intake for several reasons, including adequate total energy intake, consuming essential fatty acids, and absorbing fat-soluble vitamins.4

Falling short of your fat needs leaves you at risk of developing deficiencies that your body has to work against. Plus, while low-fat diets may help you lose weight in the short term, they typically don’t satisfy you.

4. Underlying Medical Conditions

Sometimes, weight gain is out of our control and is caused by underlying medical conditions. Many underlying health concerns can go undiagnosed for an extended period of time. For example, hidden food allergies or sensitivities can trigger inflammation. Poor gut health might also contribute to difficulties losing weight.

If losing weight is challenging despite significant lifestyle changes, consider meeting with your doctor to address potential medical implications.

5. Lack of Physical Activity

While nutrition plays a significant role in weight management efforts, it’s important to remember that sustainable results require a holistic approach. Physical activity, no matter your fitness level, is a crucial aspect of successful long-term weight loss.

The latest Physical Guidelines for Americans recommend 150 minutes of moderate-intensity physical activity per week, with two days of strength training. In addition to its role in reducing obesity, regular exercise has also been linked to reduced risk of developing type 2 diabetes, cardiovascular disease, and some cancers.5

<p class="pro-tip"><strong>Learn More: </strong><a href="are-carbs-bad-for-you">Are Carbs Bad for You? Everything You Need to Know for a Healthy Diet</a>.</p>

How to Start a Diet and Make It Work?


There’s no one-size-fits-all way to lose weight, and no two diets are the same. Consider these tips for embracing well-balanced nutrition safely and sustainably:

1. Buy Fresh Food 

Many crash diets, like the Atkins and Keto diets, demonize certain food groups, but there’s no need to eliminate specific foods entirely — unless you’re allergic to them! Instead, focus on the foods that are must-haves in your healthy diet. When possible, Incorporate fresh fruits, veggies, lean proteins, and low-fat dairy products.

To find these foods, do most of your shopping on the store's perimeter, and be mindful of what you choose while shopping the aisles. Stocking up on fresh food helps you avoid the high levels of sodium, added sugars, and trans fats that many processed options have.

2. Be Strategic About Foods With a Long Shelf Life

Many foods with a long shelf life offer little nutritional value, but that doesn’t mean you have to avoid processed foods altogether. Instead, be strategic about your food choices and always read the nutrition labels.

Foods with a long shelf life are typically high-fat and contain an array of preservatives. And while they might temporarily satisfy your cravings, long-term satiety isn’t their primary focus. Still, there are many benefits to keeping shelf-stable foods on hand — reach for the ones that offer health benefits in addition to their long shelf life. These nutrient-dense foods with a long shelf life include quinoa, oats, nut butter, prunes, and dried beans, among others.

3. Read the Ingredients

To make the most of your nutritional intake for overall health and sustained weight loss, it’s essential to be mindful of what you’re consuming. Read the ingredient lists and nutritional labels of packaged foods to help you keep track of your macronutrients. Be aware of processed foods with trans-fats and added sugars, as they don’t offer much nutritional value and can negatively affect your cholesterol and blood sugar levels, respectively.

4. Prioritize Mental Health

Nutrition changes should never come at the cost of your mental health, especially when your goal is to lose weight. Well-balanced eating is more than meal planning and portion sizes. In fact, science continues to highlight the connection between the gut and the brain, pointing to the increased importance of meeting your individualized nutrition needs.6 Fad diets aren’t designed to tailor to your specific needs, and they don’t take your mental well-being into account.

Remember that the number on the scale does not determine your worth. If weight loss is your goal, focus on a healthy lifestyle that honors the things that make you you. And remember that social media has a very skewed perspective of beauty, so don’t compare yourself to the standards you see online.

5. Healthy Thinking Around Food

It’s incredibly important to prioritize a healthy relationship with food, especially when trying to change your body weight composition. Restrictive diets often make food the enemy and can lead to a disordered view of nutrition. What may start as eating fewer calories during the day can evolve into an unhealthy restriction. And, unfortunately for some, excessive restriction can lead to overeating or binge eating, followed by feelings of shame, and back to restrictions. This vicious cycle affects your mental health and metabolic rate.

If you struggle with an eating disorder, don’t hesitate to seek guidance from a trusted counselor or registered dietitian.

6. Make Small Sustainable Changes

Goal setting is a major factor in successful weight management, and there’s a science to doing it effectively. Set SMART goals — specific, measurable, achievable, realistic, and time-oriented — to set yourself up for success as you pursue behavior changes as they relate to your weight.7
For example, if increasing your protein intake will support your weight loss goals, set a goal to eat a certain amount of protein at breakfast every day. Your registered dietitian can help you determine your nutrition needs and design goals that support your weight loss journey.

Eating Habits Matter

Well-balanced nutrition is a significant factor in sustainable weight loss efforts, but good eating habits entail more than just calories in and calories out. Healthy eating habits focus on macronutrient ratios, timing of meals, and hydration.

Avoid skipping meals and try to include a variety of foods in your diet. Prioritize lean proteins, fresh fruits and veggies, and healthy fats. Make sure you’re meeting your fiber needs and drinking enough water daily. Pay attention to your hunger cues and be mindful of your portion sizes.

If you have questions about what well-balanced nutrition looks like for you and your lifestyle, consider meeting with a registered dietitian nutritionist.

<p class="pro-tip"><strong>Also Read: </strong><a href="best-diet-for-weight-loss-2023">Best Diets For Weight Loss to Try in 2023 (Expert Approved)</a>.</p>

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Topics discussed in this article:


  1. 2018 Food and Health Survey Report - Food Insight. FoodInsight.org. (2018). https://foodinsight.org/wp-content/uploads/2018/05/2018-FHS-Report-FINAL.pdf 
  2. Ge L, Sadeghirad B, Ball GDC, et al. Comparison of dietary macronutrient patterns of 14 popular named dietary programmes for weight and cardiovascular risk factor reduction in adults: systematic review and network meta-analysis of randomised trials [published correction appears in BMJ. 2020 Aug 5;370:m3095]. BMJ. 2020;369:m696. Published 2020 Apr 1. doi:10.1136/bmj.m696
  3. Benton D, Young HA. Reducing Calorie Intake May Not Help You Lose Body Weight. Perspect Psychol Sci. 2017;12(5):703-714. doi:10.1177/1745691617690878
  4. Liu AG, Ford NA, Hu FB, Zelman KM, Mozaffarian D, Kris-Etherton PM. A healthy approach to dietary fats: understanding the science and taking action to reduce consumer confusion. Nutr J. 2017;16(1):53. Published 2017 Aug 30. doi:10.1186/s12937-017-0271-4
  5. U.S. Department of Health and Human Services. Physical Activity Guidelines for Americans, 2nd edition. Washington, DC: U.S. Department of Health and Human Services; 2018.
  6. Margolis KG, Cryan JF, Mayer EA. The Microbiota-Gut-Brain Axis: From Motility to Mood. Gastroenterology. 2021;160(5):1486-1501. doi:10.1053/j.gastro.2020.10.066
  7. Bailey RR. Goal Setting and Action Planning for Health Behavior Change. Am J Lifestyle Med. 2017;13(6):615-618. Published 2017 Sep 13. doi:10.1177/1559827617729634

About the author

Bill Tancer is a New York Times best-selling author. He is a co-founder and the chief data scientist at Signos and the creator and host of Signos’ podcast, Body Signals.

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Please note: The Signos team is committed to sharing insightful and actionable health articles that are backed by scientific research, supported by expert reviews, and vetted by experienced health editors. The Signos blog is not intended to diagnose, treat, cure or prevent any disease. If you have or suspect you have a medical problem, promptly contact your professional healthcare provider. Read more about our editorial process and content philosophy here.

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