Why Forward Won't Set a Goal Weight Below a BMI of 18.5
When you type a goal weight into Forward, it checks the number against your height before accepting it. If the goal is too low, you’ll see this:
That’s under a healthy weight for your height. The lowest we suggest is 50.4 kg.
The exact number depends on your height. Here is where it comes from, and why it’s the only place in the app where BMI shows up.
The rule
Body mass index is your weight in kilograms divided by your height in metres, squared. For adults, the CDC’s categories put underweight below 18.5 and a healthy weight from 18.5 to under 25.
Forward turns that range around and asks what weights it covers for your height. For someone 165 cm tall, a BMI of 18.5 to 24.9 is about 50.4 to 67.8 kg. A goal anywhere in that range or above it is fine. A goal below 50.4 kg isn’t, and the message tells you the lowest number we’d suggest instead.
There is one more check that runs first: the goal has to be lower than your current weight. Forward is built for losing weight, and a goal above where you are today would quietly turn the plan into something it wasn’t designed for.
If you’d like to see the range for your own height, our BMI calculator shows it under your result.
Why a floor, and not a target
BMI is a blunt tool. It can’t tell muscle from fat, so a muscular person can land in “overweight” without carrying much fat at all. The CDC describes it as a screening measure, not a diagnosis of anyone’s health. And the cutoffs don’t fit everyone equally: a WHO expert consultation found that many Asian populations face higher health risks at lower BMIs than the standard categories suggest.
So we use it in the one way it holds up well: as a simple lower limit. Forward never tells you that you “should” weigh a particular amount, and it never nudges you toward the middle of the healthy range. Where you stop is your call. The app only steps in at the bottom edge.
Why we don’t let you override it
We thought about adding a “use it anyway” button and decided against it. An app that adds up a calorie deficit every day is the wrong tool for going below a healthy weight. If that’s something you want to do, it’s a conversation for a doctor, not a setting.
It’s the same thinking behind the other limit in Forward: no pace will plan a day below 1,200 kcal for women or 1,500 kcal for men. We explain that one, and the math behind the three paces, in how big a calorie deficit should be.
Sources
- CDC: Adult BMI categories
- CDC: About body mass index
- WHO Expert Consultation, The Lancet (2004): appropriate BMI for Asian populations
This article is general information, not medical advice. Talk to a doctor or qualified health professional before changing your diet, exercise or sleep, especially if you are pregnant, have a medical condition or a history of disordered eating. See our health disclaimer.