Why Fad Diets Fail

If you’re like most people who want to lose weight, you want to lose it fast, eat the foods you like, and do it all with minimal effort. 

There are hundreds and probably even thousands of diets that check these boxes and millions of health professionals, marketers, and entrepreneurs willing to create and sell these products to you.

But the problem with fad diets is that although they may work in the short-term (weeks to months), they almost never work in the long term (months to years).

So why then, do so many people go on fad diets (and choose to follow someone else’s diet rules)?  People go on fad diets for any number of reasons but in our experience they do so because fad diets

  1. Illustrate how easy it is to lose a lot of weight by showcasing their best-case scenarios with testimonials. So and so lost 100 pounds just by doing xyz!  They don’t show the average case or all those who failed to lose any weight all at (Figure 1).
Figure 1. The individual response to any given diet varies considerably. Each circle represents one individual. A few "outliers" will lose a substantial amount of weight, most people will lose some weight, and a few people won't lose any weight at all, or even gain weight (Truby H, BMJ; 2006).
  1. Allow you to eat the foods you like without feeling deprived. For example, you can eat meat, cheese, bacon, and carb friendly candy bars on the Atkins diet.
  1. Offer well defined rules to limit the amount of thinking you must do. You can eat the food or you cannot eat the food.  There are no gray areas or ambiguity. Portion control and calorie counting (annoying, I know) are not required in some cases.
  1. They are easy to start. There is limited to no upfront or prep work. You can make an impulse decision to start the diet without considering all the work it takes to actually stick to the diet and lose weight.
  1. Take the burden off you by explaining why you’ve failed at previous diets and why this one will work. There is a compelling narrative of why the other diets and/or their practitioners are wrong.  If we only knew then what we know now they’ll say!

Fad diets do their very best to minimize the amount of thinking and effort you have to put into your diet.  Who doesn’t want that?!!  But again, the problem is that while fad diets might help you lose weight in the short-term, they almost never help you keep that weight off in the long-term.

There are many reasons why a diet might fail but we believe the primary reasons are

  1. Their dietary changes/restriction are too small. Losing weight requires a large caloric deficit (calories in < calories out) over an extended period.  Taking the stairs and cutting back on your sugar intake just isn’t going to cut it.  For example, even if a 300-pound person didn’t eat a single calorie for 8 weeks straight, they would likely only lose around 50 pounds (Table 1).  This just doesn’t seem fair, especially in light of the testimonials you see of people losing 100s of pounds of weight.  But this is reality, this is metabolism.
Table 1. Potential Weekly Weight Loss (in Pounds) at Various Daily Calorie Intakes.
  1. They don’t focus on transitions between diet periods. You can lose five pounds or more per week on a very low-calorie diet (VLCD) (<800 calories/day) of meal replacements and shakes but you can’t eat like this forever.  You need to be able to transition out of this period into a more sustainable meal pattern.  This transition is an inflection point and danger zone.  If you don’t get it right, all the work you’ve done will be undone.
  1. They are too rigid, not flexible. Research shows that people most successful in losing weight and keeping it off are flexible in their eating approach.  They can think on their feet and change on the fly.  The rigidity of fad diets (you can’t eat carbs) is not sustainable in the long-term.  Over time you are going to lose motivation and you will continually be tempted with foods you “aren’t” supposed to eat.  How are you going to deal with these situations if you haven’t prepared for them?
  1. They try to mix health and weight loss. Eating for health and eating for weight loss should be two different things, yet dietitians (and others) continually try to mix the two.  Eating for health requires many rules and many nuances.  Trying to incorporate these rules and nuances into weight loss just doesn’t make sense.  It makes things too overly complicated and difficult to follow.  Eating for weight loss isn’t inherently unhealthy, especially compared to how you have been eating and requires a few months out of the many years of your adult life.  Lose the weight first and then you can focus more on refining your diet to eat healthy.
  1. There is not enough focus on the fundamentals – meal planning, recipes, and cooking. Diet type does not really matter.  You can lose weight on an ice cream diet, a McDonalds diet or even a potato diet.  Provided you meal plan and count calories you are going to lose weight.  Fad diets work when the fundamentals are practiced.  They fail miserably when you don’t.
  1. There is no weight maintenance plan. Diets should contain a weight loss phase in which you are actively losing weight and a weight maintenance phase when you are trying to maintain your weight.  The problem is that diets only have a weight loss phase.  People think, “I lost the weight, I’m all done”.  Or I’ll just do a “softer” version of my current diet.  That’s not the case at all.  Successful weight loss requires you to continue to watch what you eat (in some fashion) the rest of your life. 
  1. They focus on food and physiology, not the individual’s life. Fad diets focus on the type of food you are eating or your body’s physiology (i.e., metabolism).  Food and physiology do not really matter.  The same person could lose weight on a low-carb/high fat diet or a high-carb/low-fat diet (Figure 1).  The idea that you need to match food and physiology is baloney.  What is important is that you meal plan around your life.  Are you single, married, have kids, work a lot, travel for work, care for an ailing family member, hate cooking, love cooking?  It is important that you plan around the unique and ever-changing details of your life.  Diets that focus on food or physiology do not do that.

Lifestyle Reboot doesn’t have some super scientific, magic secret sauce for losing weight but we do address each and every one of these shortfalls common to fad diets.  We have scoured the scientific literature and incorporated common sense practices that we’ve learned from our experiences in working with clients. 

In our next section, we would like to convince you why a comprehensive, systematic strategy employing hard work and relentless execution is what it takes to lose weight and keep it off once and for all!