Do Diets Work? If Not, Now What?

“Do diets really work?” seems to be the million dollar question. Such a complex question deserves a thoughtful and nuanced response. In this post I’ll be defining the term “diet”, outlining some of the history and original purpose of this infamous word, breaking down what the research says about the safety and feasibility of diets and concluding with what other options might be out there. 

I’d appreciate your generosity as I attempt to outline this controversial topic. I’d also like to acknowledge that I live with thin privilege (in a small, socially accepted body) and cannot fully understand the challenges people in larger bodies face on a daily basis.

Defining “Diet”

We have to come to an agreement about this infamous word if we’re going to communicate clearly and effectively. If you look in the dictionary, “diet” has traditionally meant two different things: (1) “the kinds of food that a person, animal, or community habitually eats” or (2) “a special course of food to which one restricts oneself, either to lose weight or for medical reasons.”

These two definitions yield incredibly different eating outcomes. The former simply describes “what someone eats” and the latter implies that some sort of intentional restriction is taking place. For the sake of this conversation, when we say “diet” we’re talking about the second definition where individuals intentionally restrict their food choices in order to lose weight or “improve” their health in some way. (I use quotations because it’s often assumed that weight loss equals improvements in health, and that may not always be true.) Take note of these reasons because we’ll circle back to see if these two perceived outcomes are possible. 

Altering food choices for medical reasons is a different ball-game and can be necessary in certain circumstances (though in those cases it’s still more what people can eat versus how much); we’re going to stick with analyzing the outcomes of people who voluntarily adhere to a specific diet in order to lose weight but are not medically required because of an allergy, medication contraindications, a GI disorder or other intolerance.

History and Purpose of Diets

Though most of us have come to understand the purpose of diets as a necessary means to improve our health, I was interested to learn that diets originated purely as a way to improve one’s appearance through weight loss. The first diet book on record was William Banting’s “Letter on Corpulence,” which described how he lost weight by replacing his carbohydrate intake with meat, fish and vegetables. 

Additionally, ads from the nineteenth century boasted slogans such as: “Lose weight and look lovelier”, “Don’t be fat!” and “How attractive are you at the beach?” Understanding the motives behind these campaigns is helpful. Restrictive and/or weight loss diets were not originally aimed at improving health but as a means for improving one’s appearance. If that’s the case, why is weight loss so frequently prescribed as a way to achieve better health? And, importantly, is weight-loss achievable long-term?

What does the research say about diets?

Regardless of whether or not you believe weight loss leads to better health, it’s important to examine what the research says about dieting long-term. Even if diets did lead to better health, a lot of the research says weight loss isn’t sustainable long-term. 

Conventional wisdom about weight loss is this: if you eat less than you expend, you will lose weight. Mathematically, about 3500 calories equals one pound. To lose one pound, you must burn an extra 3500 calories. Diets promote this deficit. In theory, the belief is: if we work hard enough, we will lose weight. And many of us have tried very hard. So why doesn’t increased exercise and caloric restriction lead to weight loss in the long term? One review on dieting and restrained eating as prospective predictors of future weight gain concluded, “The prospective nature of these studies confirms that dieting at one point in time is likely to predict weight gain at a later point in time.”

Let’s further unpack what else is going on when we diet.

Set Point Theory – Set Point Theory is the theory that our body has a weight range where it feels comfortable. It’s a range, not one number, which means our weight can fluctuate throughout a lifetime. Set Point Theory helps explain why so many people who lose weight through dieting end up regaining it (sometimes plus more). It’s a feedback control mechanism that fights for you to be in a range your body naturally feels comfortable in. The hard part? We don’t get to choose our set point range.

Metabolism – Research shows that our metabolism slows when we are in starvation mode (e.g. a diet). It’s pretty genius if you think about it — our bodies want to keep us alive. When they sense a lack of resources (i.e. food), they slow down to conserve the energy they have left. Our bodies aren’t able to distinguish a real famine from a diet, so they take protective measures during both. This helps explain why it gets harder and harder to lose weight (i.e. why we hit a “plateau”) after dieting for a while. 

Weight cycling – While we’ve long associated being in a larger body with increasing our risk of CVD, type 2 diabetes and other diseases, research is now showing that weight cycling also leads to adverse health effects. What causes weight cycling? Hopping from one weight-loss diet to the next. Why would someone do that? Because research demonstrates most diets lead to short-term weight loss but after about 6 months the weight stagnates or begins to creep back up. What if we have been associating larger bodies with an increased disease risk but it’s also the weight cycling (sometimes called yo-yo dieting) that’s contributing to this risk? (Also: I’m not here to debate whether being at a higher body weight is associated with health risks. I’m more concerned about what to do about it and to prevent further health complications.)

Weight stigma – It’s hard to deny the fatphobic nature of the society we live in. Chairs, planes, escalators — so many spaces are not equipped for people in larger bodies. Not to mention the well-intended but sharply misguided thin people who often suggest to people in larger bodies that they “should lose some weight” — this is harmful for a few reasons: 

• It’s not your place to make unwarranted comments about people’s bodies. Ever. 
• You have no idea what else someone has going on in their lives. Maybe they’re struggling with an eating disorder — not everyone suffering from an eating disorder lives in an emaciated body. Maybe they are on medication that recently caused their weight to change. There are tons of reasons. 
• Shame doesn’t motivate anyone to make behavior changes, and it’s each person’s prerogative to decide if they want health to be a value. And it’s that person’s decision to seek guidance from a healthcare provider. Regardless of body size, everyone deserves compassionate, ethical care from providers who won’t dismiss their comments about what they need to pursue better health. 

Psychological Trauma – Food is rooted in tradition and joy, and restriction leaves some people with psychological damage. Diets often lead to an unhealthy preoccupation with food, anxiety around eating, interference with social events and mealtimes, and an increased risk for eating disorders.

No Diet, Now What?

That was a lot of information. Based on the lack of efficacy of diets and their contributions to weight cycling and weight stigma, it’s clear that using diets as a way to improve people’s psychological and physical health isn’t helpful or ethical. 

The good news is that you get to decide, given all this information, if you still want to pursue a diet or not. It’s totally up to you. If you don’t, there are other options to improve a person’s health regardless of their body size. Healthcare professionals care a lot about improving the health and well-being of their patients, and focusing on behaviors instead of weight loss is a great way to implement healthier behaviors for the long-term. Research shows that prioritizing well-being over weight loss can lead to improvements in physiological and psychological measures.

Lastly, mindful and Intuitive eating practices have been associated with improved self-esteem and health biomarkers. These eating styles have also been associated with a decrease in binge eating, external eating and emotional eating.

There’s so much more research and nuance to add, but I’ll stop for now. Thanks for taking the time to read. I appreciate your thoughtfulness about this topic.