Why today's rapid weight loss diets always seem to fail

May 15, 2018 by Colin Poitras, University of Connecticut
Credit: CC0 Public Domain

When it comes to losing weight these days, everyone seems to be in a rush. Some of today's most popular weight loss programs promise significant weight loss in as little as 30 days or less. While many folks will succeed in losing weight initially, sustaining that weight loss over time is a different challenge entirely. UConn professor of pharmacy practice C. Michael White explored some of the research behind these weight loss programs and offers what he believes is a more practical approach to long-term, sustainable weight loss in a new book, "The Part-Time Diet – Conquering the Weight Loss Plateau." White recently sat down with UConn Today to discuss his findings and why today's popular fad diets always seem to fail.

Q: Your background and professional expertise is in pharmacy. What compelled you to look into weight loss?

A: My focus has always been on patients with heart disease and things that either cause or prevent it. Losing weight reduces osteoarthritis pain, blood pressure, cholesterol levels, and blood sugars. However, lasting weight loss is elusive and the inability to lose weight plagues people's psyches. The internet is full of stories of people who start out losing weight but weight loss eventually trickles down to nothing, leaving them demoralized. They likely represent millions of people who want to lose weight but cannot. I needed to know why this was and what, if anything, could be done about it. I did not intend to write a book. However, when I discovered why diets fail, I realized many of the current fad diets actually prevent long-term benefits. At that point, I knew I should try to get the word out.

Q: So why do so many of these diets fail?

A: No diet supports sustainable weight loss without self-denial and sacrifice. However, when you diet too hard and sacrifice too much, your body goes into survival mode and starts altering thyroid hormone and cannibalizing muscle. Your body learns to survive on fewer calories than it had in the past. Even though you may be cutting a significant number of calories, the impact of those fewer calories starts to diminish. This is what I call the "weight loss plateau." You have reached a point where you still feel all of the pain associated with a severely restricted diet, but your reward is much less because your metabolism is in survival mode and your body is actively fighting to preserve the fat cells you're trying to lose! We tend to get so fixated on the first 30-day results that we don't appreciate how going too hard for too long can really hurt your ability to lose weight over the long-term. This is true regardless of whether you are eating low carb, high carb, low fat, high fat, or like a caveman.

Q: So is there a better way to promote long-term weight loss?

A: I think there is. By engaging in what I call "part-time " instead of dieting continuously, you can help prevent survival mode and the weight loss plateau from occurring. This keeps your metabolism healthier and your muscle intact over the long-term, allowing for longer-term weight loss. Keeping your metabolism invigorated and your muscle mass healthy as you diet also helps you maintain your body weight once you stop dieting.

Q: What exactly do you mean by 'part-time dieting'?

A: In a nutshell, part-time dieting involves actively dieting for a period of time and then resting. By rest, I mean you eat enough calories to neither gain nor lose weight during your resting period. The best trials to date keep the dietary rest days of equal length to the active dieting periods, so it could be one day on your diet and one day off or two weeks on and two weeks off. Just don't diet for more than four weeks in a row; that is when the biggest metabolism damage occurs.

Q: In addition to laying out the framework of a part-time dieting plan, you considered the psychology of weight loss and probed some of the science involved in different popular weight loss programs. What did you learn?

A: Once you minimize the biological barriers to long-term weight loss, the mental factors that impede sustained weight loss become even more important. Many of these short-term diets don't address the psychological components involved with weight loss. They don't force people to come to grips with how their relationship with food and sleep impacts their ability to achieve and maintain a healthy weight over the long term. In addition, people are inundated by so many contradictory health messages that it is hard for them to decide which one might be best for their needs. Should they eat one meal a day (intermittent fasting) or six smaller meals a day? Should they primarily eat meat or should they go vegetarian? Should they go low carb-high fat or high carb-low fat? I explored all of these topics and other sacred cows of weight to see the scientific evidence behind them. In human trials, all the major diets – low carb-high fat, high carb-low fat, caveman eating, and vegetarian-based diets – have about the same impact over the longer term. That doesn't mean that one person won't do better than another if a particular plan works really well for them. But overall, it is a wash. The good news is that the part-time dieting approach can be applied regardless of the type of eating plan you settle on, and can extend the viability of that approach.

Q: There are a lot of dieting programs out there making bold promises for weight loss. What can people do to make sure they are choosing the right one for them?

A: If people are serious about losing weight – and if they're dieting they certainly are – then they should be wary of fad diets that promise too much too soon. True sustained is much more likely to happen gradually over time, not in two weeks or 30 days. Be the tortoise, not the hare. The best diets are those that are based on evidence-based science and data from randomized controlled trials. Take your time. Understand what you are getting into and what kind of commitment is involved. To me, the part-time approach makes the most sense, is clearly based on science, and is most sustainable. My hope is that this approach will encourage others to reduce their and lead happier, healthier lives.

Explore further: Taking a break from dieting may improve weight loss

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