We often get asked the question, “What’s the best diet?” While there are quite a few effective nutrition programs out there, the truth is that there’s not necessarily a single, universal “best” option. In fact, in a recent article published in the prestigious Journal of the American Medical Association, researchers compared various popular diets differing in macronutrient composition, and they found that differences in weight loss and metabolic risk factors were small (i.e., less than a couple of pounds) and inconsistent.

What they did find, however, was that the single-most important factor influencing weight loss and improvements overall health (i.e., disease-risk outcomes) was adherence, or the ability of folks to stick with a program and consistently meet program goals for diet and physical activity.

With that in mind, what does seem to be important is consistency, and that is directly tied to finding an approach to which you can stick. In addition to consistency, two of the most important factors of a successful nutrition plan are food quality (mostly whole, minimally-processed foods) and food quantity (that matches your goals, needs, body type, and activity levels). In other words, food choices and portion sizes play a tremendous role in getting healthy and losing body fat.

Unfortunately, consistently show that overweight folks are unable to adequately estimate portion sizes. It doesn’t take a rocket scientist to figure out that this inability to estimate proper food quantity results in excessive food intake, which then blunts overall weight loss.

In randomized controlled trials, we see it all the time; participants consistently under-report their food intake. In fact, in one study published in the Journal of the American Dietetic Association, 49% of participants under-estimated their food intake by an average of 21%—that’s anywhere between 300 – 500 calories, which is easily enough to halt fat loss.

Alas, there’s good news. Liquid meal replacements and portion-controlled prepackaged foods are scientifically supported strategies that can help promote weight loss and weight control. Not only do they provide portion-controlled alternatives, they also increase convenience and reduce the complexity of meal planning and decision making. Those are enormous factors when it comes to adherence (i.e., consistency).

In a brand new randomized controlled trial published in the journal Obesity, researchers from UCSD sought out to test whether providing portion-controlled prepackaged lunch and dinner entrees within a behavioral weight loss intervention promotes greater weight loss after 12 weeks compared to self-selected foods in 183 overweight adults. After 3 months, all participants lost weight; however, the group of folks who consumed two prepackaged meals per day lost 43% more weight than those who ate self-selected meals.

With that in mind, it’s important to point out that not all prepackaged meals are created nutritionally equivalent. In fact, the average portion-controlled meal that you’ll find in your grocery store freezer is likely to contain a laundry list of unhealthy ingredients including trans fats, refined vegetable/seed oils (e.g., soybean, corn, canola, safflower, sunflower), added sugar (e.g., high-fructose corn syrup), potential food sensitivities (e.g., gluten, soy protein), and even artificial sweeteners.

Fortunately, there are better options. For instance, you can practice one of the food prep rituals that we discussed in a previous newsletter and prepare your own portion-controlled meals by putting them in containers. Alternatively, there are more and more self-serve take-out restaurants and food shops popping up all over the place that provide fresh, portion-controlled, health-minded meals and snacks.