When you get right down to it, weight loss is a simple mathematical equation. It's math because it's rooted in biology, which is rooted in physics, which runs on laws that cannot be violated by basic humanity.
It all comes down to calories. Everything you eat provides you with calories of energy. Nutrients, vitamins, minerals; they're all necessary to fuel the body, but calories are the energy your body uses for everything else. The protein, the carbohydrates, the sugars, it's all fuel.
To maintain equilibrium at your current weight, you need to be burning energy at a rate equivalent to the energy you're consuming. If you burn 2,000 calories in a day, and you eat 2,000 calories in a day, you're neither going to lose nor gain weight.
There are two ways to lose weight. You can reduce the number of calories you take in, or you can increase the number of calories you burn. That's it. Every diet, every workout plan, every supplement, it all exists just to adjust this equation.
Supplements in particular play with the equation in different ways. Some of them include stimulants like caffeine, which gives you energy and helps your body burn more calories. Some of them include appetite suppressants, which help you feel full and reduce cravings for food, so you take in fewer calories in a day.
Some of them affect digestion. They might make food linger in your digestive system, making you feel full longer so you don't eat as much, reducing caloric intake. Others might block your body's ability to absorb some nutrients, making the food you eat give you less energy, reducing the calories you're taking in.
Where do meal replacement shakes land? It all depends on the shake in question. Many of them are simple nutrient-dense, energy-packed shakes that are meant to give you a meal's worth of calories in one sitting. Others include caffeine, sugar, and other stimulants to give you energy to help encouraging burning calories. Many of them include plenty of fiber, to help you feel full and minimize cravings for additional food.
Maybe you've started trying to lose weight, and one of the ways you're doing it is with meal replacement shakes. You can kick it old-school with the classic slim-fast, or you can try any of the newer meal replacements, like Ample, Huel, Soylent, and others. You've been at it for a few days, weeks, or months, and maybe you lost some weight or maybe you didn't. Either way, you're not now, so what gives? Here are the possible reasons why you might not be losing weight the way you want to.
You've Reached a Weight Plateau
One of the most common issues with a sustained weight loss campaign is a weight loss plateau. A plateau happens when you're losing weight for a while, and then suddenly stop losing weight, even though nothing has changed in your diet or your exercise routine to cause it. What causes it, though?
When you're first starting to lose weight, your body starts expending reserve stores of glycogen, a type of fat that is mostly made up of sugar and water. As you burn this energy, your body loses weight rapidly, because it's easy to get rid of excess water. You've probably noticed that you're peeing more than normal when you first start trying to lose weight; that's why.
Once you reach a point where the easy-to-lose fat is burned, your body starts turning to the harder to burn fats and muscle tissues. Burning these provides less energy, so it becomes a little harder to lose weight with it. It also means your metabolism decreases. Since your metabolism guides how much energy you're using, a decreased metabolism means burning fewer calories.
Eventually these two effects will reach a balance point. That's the plateau; your caloric burning has dropped while your reduced intake has stabilized, leaving you unable to lose more weight.
There are, of course, two ways to push past this plateau. You can further reduce your caloric intake, but depending on how much you're eating, this can be dangerous. People need a bare minimum too survive, and if you eat too little, you might experience symptoms of malnutrition.
The other way is to add or ramp up exercise to push past the plateau. Increasing exercise means you build muscle rather than burn it, and it means that you're going to be expending even more energy compared to your caloric intake. This is why a workout plan might start with a few exercises at a few reps each, but will ramp up week over week until you're working out for an hour or two every day, if not longer, with increasingly difficult and sustained effort.
You Haven't Been Taking it Long Enough
Weight loss is not instant. It takes some time for your body to adjust to a "new normal" when you start a diet plan. You may lose some weight immediately, but if you monitor your weight, you probably notice that it varies up and down by a few pounds on a daily basis just based on normal physical activity and eating habits.
Weight loss is often a long, slow process. A deficit of 500 calories per day – that is, burning 500 more calories per day than you take in – is required to lose a single pound in a week. One pound is roughly 3,500 calories, after all.
A diet and exercise plan can start showing some results within a few weeks or a month. If you haven't been consuming your meal replacement shakes for at least a month, you're probably not going to see much in the way of noticeable returns. Even worse, if you're expecting to shed the pounds rapidly, you're going to need to do a lot more than just cut 500 calories from your diet.
The average diet ideal is around 2,000 to 2,500 calories per day, depending on gender and level of physical activity. Cutting even just 3,500 per week can be difficult and can leave you with cravings, fatigue, headaches, and other issues.
Unless you're cutting down to a dangerous starvation diet, your weight loss is by necessity going to be slow going. Keep at it, keep your caloric intake low, and bolster your potential weight loss with more physical activity.
You're Not Cutting Enough Calories
One of the biggest mistakes we see with meal replacement shakes is using them as a complete meal replacement, rather than a caloric reduction.
If you're used to eating a meal that's around 400 calories, and you start replacing that meal with a 400 calorie meal replacement shake, what's going to happen?
Well, if you're lucky, you'll lose a little bit of weight and see a few health issues clear up. This might happen because the meal replacement shake is packed with vitamins, nutrients, minerals, and other beneficial ingredients, while the meal you were eating before may have been full of preservatives, processed flours and sugars, and other synthetics that don't play nice with the body. A reduction in harmful ingredients can also help stabilize hormones and improve your body's control over itself, and can result in some minor weight loss.
That said, remember that it always comes back to calories in and calories out. If you replace 400 calories in with a different form of 400 calories in, you're not actually reducing anything, so you're not going to lose weight. There's no way around it; it's simple math.
You're Cutting Too Many Calories
Cutting calories can have a dark side. As you cut more and more calories, you start encouraging your body to tap into its reserves of fat to maintain energy levels. Did you ever stop to think about why your body has that process in the first place?
Ancient humans didn't eat a consistent three meals a day. Often times they foraged for naturally-available food, mostly plant-based, and ate larger protein-packed meals when a hunt was successful. This feast-or-famine lifestyle evened out once agriculture was developed, but the body's means of adapting to it lingers on.
When you don't eat a consistent caloric intake, but you have a consistent caloric expenditure, you run into issues. Humans need the energy to hunt even when times are scarce, and the body stores that energy in fat throughout the body. When you eat a lot, you pack on the pounds, as reserve energy for when you're not able to eat but still need to burn energy to survive.
What does all this have to do with modern dieting? Well, if you diet too much, cutting too many calories, your body can go into the often-debated famine mode. In this mode, your body dials back the energy it burns, because it intuits that you're going through a famine mode and will need that energy later. This means you burn fewer calories and thus won't lose weight. At the same time, your body wants to store up what energy it gets, so more of the calories you take in are converted into fat and stored. If your metabolism slows down to burn less calories and keep you alive, you'll burn less calories and it will be harder to lose weight.
This is part of why malnutrition can co-exist with obesity, by the way. When your body lacks vitamins and minerals but has plenty of calories, it can't do anything with that energy but store it.
You're Compensating by Eating Worse
Another common issue with meal replacement shakes is the cravings. Not just cravings in general, but cravings for specific things. If you're using a meal replacement shake to replace what would normally be unhealthy meals like fast food and other heavily processed, sugar-infused foods, your body is going to crave them.
In some cases, it's psychological. You really like salty snacks but you don't get to have them on your diet, so when you get the chance to eat something other than a meal shake, you pack in the things you've been missing.
In other cases it's actually addiction. Sugar is an addictive substance with psychological and physiological effects when you cut it off. This is why, when you're dieting, you'll often crave sweet treats more than anything.
If you compensate by using cheat days or other meals to pack in these snacks and sate these cravings, chances are pretty good that your meal replacement shakes aren't actually helping you lose weight at all.
You're Adding Too Much to It
We get it; meal replacement shakes can be bland, especially if the one you're trying only has three or four flavors and you're trying to drink a shake every day. You quickly get tired of the same old flavors, so you look for ingredients to blend in to enhance their flavors. We've even given you ideas.
The thing is, everything you add to a meal replacement shake is going to add calories as well as flavor. If you've gotten into the habit of adding stuff, even healthy stuff, to your shakes, you may be increasing your caloric intake more than you realize. This can lead to throwing off your calculations and you not burning as many calories as you think you should be. Dial back on the additives and you should see a gradual increase to your weight loss.
You're Building Muscle While Losing Weight
Another common cause of a plateau, where you stop losing weight, is the fact that you're building muscle while you're working out and dieting. Muscle is not weightless, and does not weight the same amount as fat. Burning fat and building muscle can balance each other out.
In this case, it's not a bad thing that you're not losing weight; you may still be seeing changes in your body that will be visible if you keep it up. You will be losing fat and gaining muscle, which gives your body more strength and more definition. Keep up your diet and exercise, and you'll continue burning fat until you have a wonderfully fit body, even though your weight hasn't changed.