Your basal metabolic rate
Your basal metabolic rate is the energy your body needs at complete rest. HabitHelm calculates it with the Mifflin-St Jeor equation from weight, height, age and sex. A systematic review compared four common equations. Mifflin-St Jeor was most often within 10 percent of the measured value (Frankenfield et al. 2005). For an individual it can still be clearly off.
From basal rate to daily needs
For everyday life without training, HabitHelm multiplies the basal rate by an activity factor between 1.2 (sedentary) and 1.9 (very physically active). These factors are a common rule of thumb, not a recommendation of a scientific society. The FAO uses 1.4 to 1.69 for a sedentary lifestyle, but that already includes some exercise. HabitHelm adds training separately, so the factor starts lower.
How fast to lose weight?
The German S3 guideline on obesity names a deficit of about 500 kcal a day. That gives about 0.5 kg of weight loss per week. To keep as much muscle as possible, a review on contest preparation suggests 0.5 to 1 percent of body weight per week (Helms et al. 2014). Faster loss usually costs more muscle, and the goal is harder to sustain.
HabitHelm turns your pace into a deficit like this: pace in kg per week × 7,700 kcal ÷ 7 days. The deficit is capped at 25 percent of your needs, a surplus for gaining weight at 15 percent.
Why the forecast is only a rule of thumb: 7,700 kcal per kilogram is roughly the energy content of body fat. Kevin Hall of the US National Institutes of Health showed that this rule overestimates weight loss over time (Hall 2008). As you lose weight you burn less, because your body is lighter and adapts. In the first weeks it often goes faster, because you also lose water and glycogen. Check over several weeks how your weight really develops.
Training: why not every calorie counts
Workouts from Strava, Withings or Apple Health raise your daily target. HabitHelm only credits part of them: at most 40 percent when you want to lose weight, otherwise at most 60 percent, and never more than 500 kcal a day. With less certain data, such as manually entered workouts, it is a bit less. The reason: watches often misjudge workout energy by 20 percent or more, usually too high. More in the guide How accurate are your smartwatch calories?.
Carbs and fat on training days
For carbs, HabitHelm follows the position statement of ACSM, the Academy of Nutrition and Dietetics and Dietitians of Canada (Thomas et al. 2016):
- light load: 3 to 5 g per kilogram
- moderate load, about one hour a day: 5 to 7 g
- high load, one to three hours a day: 6 to 10 g
- very high load, four to five hours a day: 8 to 12 g
Depending on the day's training energy, HabitHelm picks 3, 4, 6, 8 or 10 g per kilogram. Fat sits at 20 to 35 percent of energy, as in the same position statement. Less than 20 percent is not advisable long term, because fat-soluble vitamins and essential fatty acids can fall short.
Steps and movement
The WHO recommends 150 to 300 minutes of moderate activity per week for adults, or 75 to 150 minutes of vigorous activity, plus muscle strengthening on two days (WHO 2020). There is no official recommendation for steps. An analysis of 15 studies with more than 47,000 adults found: from age 60 the risk of death fell up to about 6,000 to 8,000 steps a day, below 60 up to about 8,000 to 10,000 (Paluch et al. 2022). Beyond that, little more was gained.
Sources
- Frankenfield D, Roth-Yousey L, Compher C (2005): Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association 105(5):775–789. doi.org/10.1016/j.jada.2005.02.005
- FAO, WHO, UNU (2004): Human energy requirements. FAO Food and Nutrition Technical Report Series 1.
- German Obesity Society: S3 guideline on prevention and therapy of obesity, AWMF register 050-001. register.awmf.org
- Helms ER, Aragon AA, Fitschen PJ (2014): Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition 11:20. pmc.ncbi.nlm.nih.gov/articles/PMC4033492
- Hall KD (2008): What is the required energy deficit per unit weight loss? International Journal of Obesity 32(3):573–576. pmc.ncbi.nlm.nih.gov/articles/PMC2376744
- Thomas DT, Erdman KA, Burke LM (2016): American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise 48(3):543–568. doi.org/10.1249/MSS.0000000000000852
- World Health Organization (2020): WHO guidelines on physical activity and sedentary behaviour. who.int
- Paluch AE, Bajpai S, Bassett DR et al. (2022): Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts. The Lancet Public Health 7(3):e219–e228. pmc.ncbi.nlm.nih.gov/articles/PMC9289978