Does keeping a food journal affect weight loss?

At NutriMirror we try not to focus on weight loss, instead preferring to promote healthy lifestyles that (as a side effect) often result in healthy changes to body weight.

But the fact remains that people who are seeking out a food journal most often do so with weight loss in mind; and people who are seeking to lose weight through any of various methods can get great value from tracking the foods they eat.

Does it work? Does keeping a food journal lead to weight loss?

Studies have repeatedly shown that, yes, it does. The accountability and awareness that comes from regularly recording the foods you eat has been shown to lead to twice as much weight loss compared with people who don’t regularly record their food intake.

We see the evidence all the time at NutriMirror, with members speaking out in the journal room and in our testimonials about the amazing success they’ve had with our system. But we’ve been doing this for quite a while now and we’ve got quite a bit of data built up, so I wanted to run some numbers and see what kinds of statistical evidence we could pull up.

The following graphic comes from a random sample of 600 NutriMirror members who have logged foods anywhere from 30 to 365 days (click the graph for a larger view):

Graph of weight loss success for food journal users

600 randomly selected users who recorded their food intake for between 30 and 365 days. Average weight change: 6.7 pounds lost.

We don’t know what the intentions were of the people in this sample group (some may have been using the system to maintain their current weight or even gain weight) but the numbers show a clear trend toward weight loss when tracking foods with NutriMirror. Some lost much more and some gained weight, but the average weight loss per person was 6.7 pounds.

Here’s a similar graph showing another 600 random users, but this time we’re selecting from a pool of long-time members—people who have logged foods with NutriMirror for more than a year.

Avg. weight change: 14.3 pounds lost.

The results here are quite similar to the first graph, just spread out a bit by a few “outlier” members who have logged a lot of days or recorded a great deal of weight loss. In this data set, 475 users lost weight, 112 gained weight, and 13 saw no weight change. The average weight loss was 14.3 pounds.

But here’s where things get really interesting. As valuable as it is to record your foods every day, for many reasons people can get bored with it or drift away for a while, and then come back to pick up where they left off. NutriMirror is a learning tool as much as anything else. Often we think of it as a helpful aid that teaches you how to eat. So people will use it for a while, then leave for a while, then come back again for a refresher course.

Anyway, I’ve taken the same data set as above, but broken each user down into separate blocks so that we could compare their net weight changes during times when they were actively logging to their net weight changes during the times they were not:

The trend here is pretty striking. Red dots indicate periods of logging inactivity, and they mostly fall below the 0-line and into the weight gain area. Green dots, representing periods of regular logging, do the opposite. Here are the averages:

  • Avg. weight change per person during periods of consistent logging: 3.3 pounds lost
  • Avg. rate of change while logging consistently: 0.3 pounds lost per week
  • Avg. weight change per person while not consistently logging: 1.2 pounds gained
  • Avg. rate of change while not logging consistently: 0.2 pounds gained per week