Feb 26 2019

Self-Monitoring for Weight Loss

The most effective method for weight loss! Lose weight in less than 15 minutes per day.

These sound like typical weight-loss overhyped sales pitches, but they are reasonably supported by evidence. There is now good (but not great) evidence that frequent and consistent self-monitoring predict successful long-term weight management. In fact, a new study finds that those who successfully used online dietary intake self-monitoring eventually spent only 14.6 minutes per day on the activity.

There are three components to self-monitoring in weight management: dietary intake monitoring, self-weighing, and exercise self-monitoring. Self-weighing probably has the best evidence so far. The evidence supports weighing yourself from every day to every week consistently as a good predictor of successful long term weight management. The optimal frequency is still a matter of debate, but it should be at least weekly. Consistency also appears to be a key.

Dietary self-monitoring is essentially estimating or counting the calories you eat each day and recording them in some fashion. Why might this be helpful? The evidence shows that people generally underestimate the calories in food and that they consume (by as much as 50% in some studies).  These studies are limited often by self-reporting, but there is a consistent result.

In fact, people both over and underestimate the caloric content of different foods, but they tend to underestimate (when they do) by more than they overestimate. In one study they overestimated by 65 calories on average, while underestimating other foods by 165 calories.

That study also found something very interesting – people consider salt, fat, and sugar content more than just calories when evaluating whether a food is “healthy.” While such considerations are important also (mainly to avoid extremes) they actually essentially don’t matter for weight management. However, there is an entire industry focusing the public’s attention on carbs and fat and distracting them from the one thing that matters for weight, calories.

If calorie estimation is so important, then does calorie food labeling help? The evidence is still unclear, mainly because its difficult to execute well-designed studies. The evidence we have so far is mixed. In a Canadian study they looked at the public’s ability to estimate calories after enforcing calorie labeling requirements in restaurants. After six months there was little effect on calorie estimation (but this might not have been long enough).

People do tend to purchase fewer calories when menus list the caloric content of specific food items. I have been there myself – shocked at how many calories are in a side of fries, for example. That is the goal – for people to use the information to reduce their caloric intake, which means purchasing less food. This, however, could be a money-loser for restaurants, so some have stopped doing it. Or they post the calories on their website, so they can say they are doing it, but they know this has no effect.

What about self-monitoring apps? This is a moving target, as the whole phenomenon of smart phones and apps is still relatively new (from the perspective of doing scientific studies). The systematic reviews still refer to studies looking at “personal data assistants.” By the time the current crop of apps are adequately studied, they will be outdated.

But the bottom line of the evidence we have so far is that they basically work, although we need better data to be sure. The predictors of success appear to be frequency and consistency. If you consistently log your calories every day, that predicts a higher chance of long term weight control.

Importantly, the amount of detail recorded does not seem to matter. There must be some critical threshold as a minimum, but it seems that any reasonable recording of calorie intake will do. Adding more detail doesn’t help.¬†This general trend fits other data, which shows that the most successful dieters lose weight slowly and steadily.

What they have in common is that success is predicted by making manageable changes to your daily routine. If you want to change your weight, you have to change your daily habits, your lifestyle. “Going on a diet” is a famously unsuccessful strategy, no matter what the diet is. All diets seems to result in a modest amount of short term weight loss following by weight regain, often more than was lost.

But if you change your eating habits in a sustainable way, then you can make sustainable changes to your weight. Forget about rapid weight loss – that is both not healthy and not sustainable. Forget about extreme regimens (I am not talking about athletes, but everyday people just trying to manage their weight). Small sustainable and permanent changes are what helps.

And the focus should be on controlling calories in. That is, the evidence shows, almost the entire game. Definitely exercise, for all the health benefits that creates, and this does help a little with weight management. But exercise alone won’t do it – you have to control calories in. You cannot do this if you are systematically underestimating your caloric intake.

I am not going to recommend any one strategy or app. Do what works for you. If you try something and it doesn’t work, try something else. And by “working” (again, assuming the goal here is weight management) I mean the pounds are coming off on the scale. That is why weight self-monitoring is also critical – whatever you are doing, if you are not losing weight, it’s not working. The scale doesn’t lie. So just keep cutting your caloric intake until you do start to consistently lose weight, for most people about a pound a week is a good target.

This again is where calorie estimation comes in. The evidence shows this does not have to be onerous. Just having a reasonably good idea how many calories are in your food is enough, and tracking how much you are actually eating.

The evidence for all of this, while not perfect, is strong enough that we can make solid recommendations. But there is a tendency in general to focus on the wrong things – to focus on gimmicky or flashy interventions, or unrealistic promises, or on anything other than what we all know we need to do – move more and eat less. The food industry and self-help industry has successfully confused the public about the basic facts. Almost everyone I know obsesses over “carbs” when, as long as you are not diabetic and eat within a reasonable range, this is essentially not a factor they need to obsess over at all.

What is sad is that the hype distracts people from what the evidence shows actually works.

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