I recently got an email from a long-term patient asking about the safety and efficacy of meal replacement shake systems. You probably think I’m going to launch into another rant, and yes that is partially true, but this one is a little bit more nuanced. That’s because if your goal is weight loss, meal replacement shakes can work and be safe. However, this comes with a LOT of qualifications. Let’s begin with a review:
Weight loss is about calories, and calories only.
When it comes to losing weight, you need to burn more calories than you take in. In the short term, about 3500 calories = 1 pound of fat loss, though this has been hotly contested recently as energy requirements change with changes in body mass (aka as you lose weight). Regardless, even if the “3500 rule” doesn’t apply for long-term losers it’s still a matter of energy deficit. Shakes help to create this energy deficit by taking the guesswork and temptation out of mealtime. You know how many calories is in your shake, and there is no fudging it: you can’t add a tiny extra sliver of pizza, you can’t accidentally add an extra tablespoon of oil to the pan – it just is what it is. Often, “what it is” is 100-200 calories, which is WAY less than your typical lunch or dinner. Hello energy deficit!
Overall health is about more than just calories.
So while you may go digging yourself this nice big energy deficit with a meal replacement shake, a shake is not food. These meal replacements are formulated specifically to ensure that you are getting enough protein, a bit of fiber, and some nutrients like vitamin C and iron, but it’s nowhere near as nutrient dense as a salad with grilled vegetables, salmon, and a whole grain roll.
Also, it’s a shake…
I’ve said it before and I’ll say it again: food is about more than just nutrition!! Can you imagine going out to lunch with a friend, passing on whatever goodies are at the restaurant, and pulling out your blender bottle? Talk about a mood killer. A better way to achieve a calorie deficit would be to reduce the calories in your meals – look for things that have a lot of volume and will sustain your satiety with few calories. You should know what I’m going to say: bump up the vegetables, friends! Include lean proteins, and a modest amount of whole grains. This way, you can eat real food (a revelation!) and still lose weight.
A look at the evidence
There has actually been a bunch of research done about meal replacements, and a lot of the studies use shakes similar to these ones for the replacement. In most studies, participants are obese or morbidly obese and are instructed to replace two or more meals with a meal replacement shake, resulting in a very low calorie diet (VLCD). These diets result in weight loss.
But do participants maintain that weight loss? The answer is yes, if they continue to stay on the shake some studies show similar maintenance compared with people on the weight loss drug Orlistat. In some cases, study participants are put on a VLCD that is achieved by complete meal replacement for the period of weight loss, and then instructed to replace one or two meals per day with the shake for weight maintenance. That has worked for many.
The evidence is sparse, however, for healthy weight people or slightly overweight people using meal replacement shakes as a means to lose a couple pounds. Thinking critically though, it would make sense that replacing one higher-calorie meal daily with a calorie-controlled meal replacement shake would result in lower calories throughout the day, and would therefore result in weight loss. If I were to suggest using a meal replacement shake to a normal or slightly overweight patient, I would suggest replacing dinner, as we often go overboard at this meal and therefore could see the most benefit with replacement.
So what should you do???
There are a bunch of factors to consider when deciding if you should invest.
1. Degree of overweight/obesity: Be honest with yourself: are you needing to lose a large amount of weight or are you just getting nitpicky about that extra 5-10 pounds that you’d “like” to see gone? Meal replacement with shakes is a good option for those with a lot to lose because they can take it off really quickly if commited to the full regimen. If you have less to lose, the money you pay to replace one meal a day may not be worth it – you can probably achieve the weight loss you’d like through lifestyle change achieve it in an acceptable time frame. By contrast, at the rate of weight loss recommended (1-2lbs per week) it could take years for a person with morbid obesity to achieve a healthy weight.
2. Previous attempts: Have you tried to lose weight with diet and exercise and you still have a long way to go? If the slow and steady weight loss produced by these methods isn’t gonna cut it, then consider meal replacement.
3. Cost: This stuff doesn’t grow on trees, y’all. Think about whether you want to invest. This is especially important for people who are not doing it for medical reasons and are just planning to incorporate one meal replacement a day or on some days – you still have the cost of food to consider, do you want to add a $45 can of powder that will make just 16 meals? For that kind of money you can have an extra big serving of Summer Harvest Salad (with tuna!).
4. Social strain: Remember when I talked about how it’s a pain in the ass to try to eat with someone who will only eat chicken fingers? It’s also a pain in the ass to try to eat with someone who will only drink shakes. I mean that with all due respect. If this is for your HEALTH, then hell yeah more power to ya! And believe me, making friend dates to do something other than eating is probably one of the healthiest things you can do for your body and your relationship. But if you’re needlessly complicating the lives of all your friends, well maybe you should just order the salad instead.
5. Post-shake plans: Like I mentioned in the research section, the success of using shakes for weight loss was highly dependent on including them in the weight maintenance phase. Do you plan to do this forever? If not, do you have a Registered Dietitian you can talk to about ways to reduce the calories of your regular meals so that your daily intake is lower than it was to get you to whatever weight you started at? You need to be responsible and think of this as a long-term thing if it’s going to work. Sure, you could gain the weight all back then go on a liquid diet again, but…it’s a shake………