Food Energy Density and Obesity: Another strategy to regulate intake
¹Jeukendrup, Asker. “The Role of Energy Density in Weight Management.”
SUPER BRIEF SUMMARY
So here’s the idea. If you eat foods that are high in volume and low in calories (aka low energy density foods) you will feel more full while eating fewer calories. This intuitively makes sense. One can understand how drinking a cup of olive oil is likely worse, when it comes to weight loss, than eating a cup of celery. However, is there data to support this method in the real world?
In a decent sized meta-analysis (lumping a bunch of studies together) by Stelmach et al, the authors demonstrate “a significant association between low energy density foods and body weight reduction, i.e., ́0.53 kg when low energy density foods were eaten (95% CI: ́0.88, ́0.19).²” Keeping in mind, 0.53 kg isn’t a ton, but this is a relatively easy modification to implement with no real harm.
A larger meta-analysis by Robinson et al demonstrated up to a 850 kcal daily deficit when participants were given only low energy density foods.³ That’s right, a 850 kcal daily deficit!
Furthermore, low-density foods tend to be less processed. As discussed in a previous blog post, eating minimally processed foods seems to be more important than the macronutrient composition itself. So, in my opinion, this method seems like a win-win-win. I will definitely add this into my toolbelt to help patients suffering from obesity.
THE WHOLE TALK
First things first, what is food energy density? It is the amount of calories in a given weight of a food. This is usually measure in kcal per a gram (or kcal/g). Different macronutrients have different energy densities as well. For example, fats have about 9 kcal/g while protein has about 4 kcal/g.
Now, the question I will aim to answer in this post, is if there is high quality evidence to demonstrate a dietary modification focusing on low density foods helps with weight loss. This certainly makes physiologic and anecdotal sense, but often things don’t pan out when these variables are actually studies.
There are two main problems with many food and nutrition studies.
They are often based on 24 hour food recall questionnaires
these are often wildly inaccurate and almost always skew to what individuals think is healthier or preferred
There are based in a lab which does not necessarily extrapolate to the real world.
However, we do have to work off of the data that we actually have. So, big grain of salt when you read about many food studies. Make sure to check how the data is collected and what the research setting is.
Now, let’s turn to some of the studies!
Every once in a while I get lucky and there is a well done and recent systematic review and meta-analysis of the topic I hope to discuss. This is one of those times! In 2022 Robinson et al did an excellent review titled “Calorie Reformulation: A Systematic Review and Meta-Analysis Examining the Effect of Manipulating Food Energy Density on Daily Energy Intake.”³ To be honest, I am going to summarize that article as they do an excellent job. So a big thank you to Robinson and team!
As a quick reminder a systematic review and meta-analysis can be defined as follows:
“A systematic review attempts to gather all available empirical research by using clearly defined, systematic methods to obtain answers to a specific question. A meta-analysis is the statistical process of analyzing and combining results from several similar studies.”⁴
Robinson ended up summarizing a total of 31 articles on the topic. Below is the forest plot that demonstrates the relative effect seen in each study when comparing diets with low energy density versus medium/high energy density. This is a very busy picture but I would like you to focus on the summary of the data at the bottom (the large black diamond outlined in red).
This demonstrates the total effect if you were to pull all the data from the separate studies into one big pool. It’s a pretty impressive.
However, there was a lot of differences between all the studies (some were only for 1 day or had different ways of manipulating the energy densities of foods served) so I am weary to put a lot of faith in the average across these studies.
Robinson broke the data down further into studies that altered the energy density of ALL foods that were served. This led to an impressive decrease of 855.85 kcal per a day. To be honest, I’m quite suspicious of this given the VERY large effect.
Probably more realistic is the comparison of studies that only altered the energy density of some of the foods served. This was still a large effect at a net deficit of 237.84 kcal per a day. Still quite impressive!
As always, there are a lot of limitations to this data.
“A limitation of included studies was their relatively short duration (between 1 and 14 days). We found some inconsistent evidence that the length of time energy intake was measured for moderated findings, whereby effects of energy density on daily energy intake were smaller among studies with longer duration in our main analysis…This finding may indicate that over time consumers learn about the energy density of food served and adapt their food intake, but this adaptation is only partial.”
and finally…
“A small sub-set of studies examined change in body weight and although after being served lower vs. energy dense foods participants tended to lose more weight, this difference was not statistically significant.”
Given all this information (thank you again Robinson et al) what will I recommend to my patients? I think this is an effective way to reduce energy intake during the day. The data definitely seems to support this as a safe and efficacious intervention to decrease total daily energy intake. While there isn’t the data to definitively support this strategy will lead to actual weight loss, I interpret this more as a lack of data, NOT data demonstrating a lack of benefit.
Finally, how can you actually implement this? Well, for the most part, it’s pretty straighforward. Asker Jeukendrup summarized this well¹:
Increase variety and availability of low-energy-dense foods:
Increase intake of high-water foods
Vegetables, fruits, soups
Whole grains and legumes
Portion control/limit intake of energy-dense foods:
High-fat foods
Foods with low moisture content
Alcohol
¹Jeukendrup, Asker. “The Role of Energy Density in Weight Management.”
SOURCES
Jeukendrup, Asker. “The Role of Energy Density in Weight Management.” askerjeukendrup, March 20, 2020. https://www.mysportscience.com/post/energy-density-and-weight-management.
Stelmach-Mardas, Marta, Tomasz Rodacki, Justyna Dobrowolska-Iwanek, Anna Brzozowska, Jarosław Walkowiak, Agnieszka Wojtanowska-Krosniak, Paweł Zagrodzki, Angela Bechthold, Marcin Mardas, and Heiner Boeing. “Link between Food Energy Density and Body Weight Changes in Obese Adults.” Nutrients 8, no. 4 (April 20, 2016): 229. https://doi.org/10.3390/nu8040229.
Robinson, Eric, Mercedes Khuttan, India McFarland-Lesser, Zina Patel, and Andrew Jones. “Calorie Reformulation: A Systematic Review and Meta-Analysis Examining the Effect of Manipulating Food Energy Density on Daily Energy Intake.” The International Journal of Behavioral Nutrition and Physical Activity 19, no. 1 (April 22, 2022): 48. https://doi.org/10.1186/s12966-022-01287-z.
Ahn, EunJin, and Hyun Kang. “Introduction to Systematic Review and Meta-Analysis.” Korean Journal of Anesthesiology 71, no. 2 (April 2018): 103–12. https://doi.org/10.4097/kjae.2018.71.2.103.
