Weight goals: how your coach manages body composition

How weight management is enabled

The Weight & nutrition block appears in Coach Tuning automatically when either of these conditions is met:

• A body-composition goal. The coach recognises weight loss, muscle gain, recomposition, weight maintenance or a pre-race cut in your goals.
• A connected food diary. YAZIO or FatSecret shows Connected under Integrations.

If neither is present, a grey hint explains that the block will appear once you add a weight goal or connect a diary. Remove the goal and disconnect the tracker and the block hides, but your settings are preserved and return with the goal.

Rate-of-change presets, not arbitrary numbers

There is no free-form calorie-deficit field. You choose from three presets, each bounded by published evidence:

• Gentle — approximately 300–500 kcal/day deficit, up to 0.5% of body mass per week. Subtle and sustainable over longer periods.
• Steady — approximately 500–750 kcal/day, up to 0.75% per week. A standard, conservative rate.
• Aggressive — approximately 750–1,000 kcal/day, up to 1% per week. The upper boundary in ISSN (Aragon et al., 2017) and ACSM (Donnelly et al., 2009) guidance; adequate protein and strength training are mandatory.

For muscle gain, the presets are mirrored: a surplus of approximately 300–500 kcal and a limit of 0.5% body mass per week. Crucially, there is no setting above the safe rate. Garthe et al. (2011) illustrates why: losing around 0.7% per week preserved substantially more lean mass than losing around 1.4%. If your target number and deadline would require exceeding the limit, the coach will say that the deadline is incompatible with a safe rate and propose a safer timeline.

Medical guardrails override every setting

Weight management is integrated with the medical screening layer. These are vetoes, not suggestions — just like injury constraints elsewhere in Coach Tuning:

• Red screening status, a critical medical flag without physician clearance, or pregnancy disables active weight management entirely: only light training and a discussion about medical clearance.
• Low ferritin or haemoglobin limits the plan to Gentle, with a focus on iron and protein.
• Diabetes limits the plan to Gentle and explicitly advises consulting an endocrinologist.
• A history of disordered eating identified during screening disables proactive weight comments unless you re-enable them; the coach responds only when you raise the subject.

If a rate is currently unavailable, its button is replaced by a grey chip explaining why — for example, Unavailable: ferritin below range. The coach explains the constraint rather than simply refusing.

If a rate is formally available but your lab results are outdated, selecting Aggressive opens a panel recommending specific tests: a complete blood count with ferritin, TSH and T3, vitamin D, the hormonal axis, glucose/HbA1c and lipids, plus ALT/AST and creatinine — aligned with the IOC RED-S consensus (BJSM 2023). You can upload results, return to Steady or select Enable anyway. The coach does not block your decision, but records that it was made without recent data and monitors you more closely.

RED-S (Relative Energy Deficiency in Sport): a warning that cannot be ignored

During an active deficit, the coach monitors energy availability: energy intake from your diary minus exercise energy expenditure, relative to fat-free mass. If it remains below approximately 30 kcal/kg FFM for several days — the IOC warning threshold for Relative Energy Deficiency in Sport — a low-energy-availability flag joins suppressed HRV and poor sleep in the alerting pipeline. The plan becomes more conservative and the coach addresses the trade-off directly: increase intake or reduce training.

Weight itself is assessed only as a weekly trend using a seven-day average. Daily fluctuations from water are noise, not progress, and are not treated as such.

Food diary: YAZIO or FatSecret

Accurate energy-availability analysis requires intake data, so connecting a food diary is the logical next step for a weight goal. The coach imports daily calories and macros, while your latest weigh-in updates your profile and trend. Connect under Integrations: credentials are used once to obtain technical access tokens and are never stored. Data then updates through a nightly sync and the Sync now button. See YAZIO and FatSecret for details. Nutrition integrations require Pro.

Without a diary, the coach works only with expenditure: you enter weight manually and nutrition guidance remains general and protocol-based.

Where this appears in the product

• Today — Energy · balance. Seven days of paired expenditure/intake bars, a Yesterday summary and a weekly deficit chip in kcal. Estimates are marked ≈ with an accuracy note.
• Session analysis. Device-measured calories are shown directly; MET-based estimates carry a (?) marker and a 15–20% error disclaimer.
• Coach Tuning. Weight & nutrition includes rate presets and proactive-coaching controls — On request only / Notice and suggest / Actively manage, with the latter two on Pro — plus a Weight-rate card with an estimated goal date.
• Habits. One-tap presets include a morning fasted weigh-in 3–4 times per week, protein at every meal and carbohydrate around training.
• Chat. Weight and nutrition answers are generated only after retrieval from the knowledge base, with author and year cited rather than relying on model memory.

The evidence behind it

The coach’s library includes specialist material on this subject: Matt Fitzgerald’s Racing Weight on endurance-athlete body composition, Asker Jeukendrup’s Sport Nutrition, Borisova’s Sports Nutrition for Athletes, and monographs on physiology and recovery. It also contains dozens of papers, from the ACSM position stand (Donnelly et al., 2009) and Garthe et al.’s 2011 study of weight-loss rates in athletes to the 2023 IOC RED-S consensus. Every weight-related recommendation cites a specific source. On Pro, you can add your own book and increase its weighting so the coach prioritises the methodology and literature you trust.

Do I have to keep a food diary?

No. Rate limits, weight trends and all medical guardrails still work without one. However, adjustments become less precise: the coach cannot tell whether a plateau is caused by underfueling rather than excessive training load.

Why can’t I choose a faster rate?

Because these limits reflect physiology, not marketing. Above roughly 1% of body mass per week, a greater share of the loss comes from lean tissue, hormonal function deteriorates and RED-S risk rises. There is deliberately no above-the-limit control — just as a responsible human coach would not offer one.

What is energy availability in plain English?

It is the energy left for basic physiological function and recovery after the cost of training is subtracted. Sustained availability below approximately 30 kcal per kilogram of fat-free mass forces the body to economise on immunity, hormones and bone health. That is why the coach monitors it as closely as HRV.

Can I simply maintain my weight?

Yes. Maintenance is a distinct goal: conservative limits, a stable weight trend and nutrition matched to training load are the priorities.