The concept of switching onto powdered food for an extended period of time (3 months if you do the Habitual programme) is a daunting one, and often comes with lots of questions, including whether or not it’s safe and healthy to exist on 800 calories per day for that long. The short answer is yes—it’s completely safe and this has been confirmed over years of clinical research. But if you’re still wanting more evidence, here it is.

A refresher: What is total diet replacement (TDR)?

Total diet replacement, often referred to as TDR, is a nutritionally-complete, powdered diet of shakes, soups, and porridges that is used for weight loss.

TDR programmes can vary in terms of the total calories and number of sachets per day: We use 4 sachets of 200kcal each for a total of 800kcal per day. Each sachet, regardless of the flavour, contains exactly ¼ of the micro and macronutrients your body needs… meaning you get 100% of your nutrient needs every day.

TDR has been shown to be an effective tool for losing an average of 15kg of weight and, in many cases, leading to remission of type 2 diabetes.

Total diet replacement regulations

The first thing to know when it comes to TDR safety is that TDR products are regulated in the EU to ensure that they are safe for those consuming them. So if a company claims that their products are “total diet replacement”, they are legally obligated to ensure that both micro and macronutrient levels are met.

It’s important to know that “meal replacements” are not the same as total diet replacement. Meal replacement products are much more readily available (there are likely dozens of options in your local pharmacy), however the nutrient content in them is not sufficient to be used as a complete replacement of a diet. So while it’s perfectly fine to use meal replacement products as, well, a meal replacement (for example, a shake for breakfast instead of eggs and toast), it’s not  safe to use them as your only food intake.

TDR safety: Seeing your doctor

If you are planning to do a total diet replacement programme, you should see your GP before starting. This is particularly important if you take medications for high blood pressure or diabetes, as these medications may need to be adjusted for your safety.

Is it safe to eat only 800kcal per day?

According to the TDR regulations, only products that provide a daily total of between 600 to 1200kcal qualify as total diet replacement. As we said above, in the Habitual programme we use products that total to 800kcal per day, which is the same as was used in the world’s largest diabetes reversal trial using TDR.

The reason that TDR is so effective at inducing weight loss is that it creates a significant calorie deficit whilst maintaining nutritional-completeness. And while going down to 800kcal is a big jump from, say, 2,000kcal per day, the evidence shows that it is completely safe to do so.

The one thing to note here is that this only applies to people with a BMI of less than 40. Because people with higher BMIs burn more calories at rest, it is recommended to slowly taper down onto 800kcal per day if your BMI is over 40.

Total diet replacement is nutritionally-complete

As mentioned above, total diet replacement is a nutritionally-complete food product, and for many people may actually be more complete than their current diet, despite being much lower in calories.

This is part of the reason that TDR acts as such an effective physical and mental reset: For three months, you won’t have to think about making food choices or worry about being healthy. All of your nutrients will be taken care of, and there’s no calorie-counting to be done!

Many of our patients tell us that TDR also resets their tastes—from craving fruit for the first time to enjoying vegetables they never before would have touched.

How to safety switch back to a normal diet after TDR

One of the issues with traditional TDR programmes is that they tend to lead to weight regain, because they don’t help you to re-introduce healthy foods back into your diet. While it’s not dangerous per se to start eating a normal diet straight after completing a stint of TDR, the best evidence for maintained weight loss after TDR is for programmes that slowly add normal foods and calories to your daily intake, rather than all at once.

In the Habitual programme, we spend as much time reintroducing food as we do on TDR, and we use those three months to help you understand how various foods impact your body and your health. By the end of the Habitual programme you’ll not only be an expert on the latest nutritional science: You’ll also have the tools and new habits to help you make healthy eating your new normal.