A downloadable mod

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Last updated: v2.0.3.1, 15th March 2023
Working for The Sims 4 v1.96.365, The Infants Patch, 14th March 2023
Also compatible with The Sims 4 Legacy Edition

What it does
This mod is a bundle of tweaks and options for you to control the fat and muscle changes of your sims. Through a handy in-game settings menu, you can: 

  • Make the rate of change of all sims' fat and muscle slower (or faster).
  • Prevent all fat and muscle changes for sims not in the active household.
  • Expand the limits for sims' fat and muscle levels, allowing them to become heavier, leaner, or more muscular.
  • Apply a fix for all teens becoming underweight.
  • Remove the slower fat and muscle decay from sims with the 'High Metabolism' trait.

Why would you want this?
Fat and muscle changes in an unmodded The Sims 4 are tuned to be very fast, so you can see immediate results after exercise. If you play on longer lifespans, or would like a subtler fitness feature, or like the idea of sims' bodies changing more realistically, you might want this mod's Fitness Changes Multiplier feature to slow things down.

In an unmodded game, the background sims that eat from food stalls and go the gym will have their fat and muscle change from the things they do while in your neighborhood. This can lead them to quickly get extreme bodies, if most of their on-screen time is spent exercising or eating. If you play on longer lifespans, or with aging off for non-played sims, this problem becomes worse. If you switch households a lot, this can affect your own played sims while they are out of your control. Using this mod's No NPC Fitness Change feature can solve this issue while still letting your played sims be affected by fitness while you are playing with them.

If you'd like your sims to be able to grow and change into a wider variety of body shapes than the base game allows, you might want the Expanded Fitness Limits feature.

Sims modder Candyd discovered that in an unmodded game, teens have a modifier applied to them that halves all of their fat gains, but has no effect on their fat losses. If you've noticed that your teens typically end up at low fat by the time they become adults, regardless of exercise, this will be why. If you want to try teens with normal adult metabolism, you might want this mod's Underweight Teen Fix feature.

If you want to give a sim the Bodybuilder aspiration, but don't want them to rapidly change from the body shape you gave them in Create A Sim, you might want the No High Metabolism feature to disable the High Metabolism trait's modifier to fat and muscle decay.

How to use 

To access the settings for this mod, click on your active sim, open the 'roBurky' category, and choose 'Fitness Controls'.

From this settings menu, you can decide which features of the mod you wish to use.

  • Fitness Changes Multiplier
    • Defaults to 1.0
    • All fat and muscle changes for all sims will be multiplied by this value. When set to 1.0, the feature is disabled. When set lower than 1.0, changes will be slower. When set higher than 1.0, changes will be faster. 
    • Set to 0.0 to prevent all fat and muscle changes for all sims.
    • Set to 0.2 or 0.1 to recreate the effects of Candyd's Retuned Metabolism mod.
    • I'm going to be testing a value of 0.33 for my own game.
  • No NPC Fitness Change
    • Defaults to ENABLED
    • When enabled, the fat and muscle of sims will change only when they are in the active household. This works by applying a 0x modifier on fat and muscle changes for non-played sims.

  • Underweight Teen Fix
    • Defaults to ENABLED
    • When enabled, teens will gain and lose fat at the same rate as adults. This works by removing the 0.5x modifier on fat gains for teens.
  • No High Metabolism
    • Defaults to DISABLED
    • When enabled, the fat and muscle of sims with the 'High Metabolism' trait will decay normally. This works by removing the 0.5x modifier on fat and muscle decay for this trait.
    • This feature does not affect the ability of sims with the 'High Metabolism' trait to use an energy drink to become energized.

After changing any setting, you will need to restart your game before your changes will take effect.

Expanded Fitness Limits feature
With this feature, you can expand or reduce the range of sims fat and muscle levels. You can allow your sims to appear heavier, leaner, or more muscular than in the unmodded game.

The new limits apply both to the body sliders in Create-A-Sim, and to fitness changes from eating or exercise in live-mode. Sims' visible physique should continue to change at the same rate as before. Other effects from reaching high or low fat or muscle should take effect at the same visible level as before. Everything should behave almost exactly as you would expect.

Fitness Limits preset packages
To use the new limits, you should choose ONE optional limits package to download and install alongside the core Fitness Controls mod. The preset packages available to choose from are:

  • 1.75x - Increased
    • This preset provides increased limits that should still appear believable, and should not cause issues with animations.
    • Limits - Heavy: 1.75x / Lean: 1.00x / Fit: 1.75x / Bony: 1.00x
    • The images of sims on this page were made using this preset.
  • 3.00x - Exaggerated
    • This preset provides exaggerated limits that can appear cartoonish, but should not distort the sim mesh beyond its breaking points.
    • Limits - Heavy: 3.00x / Lean: 1.00x / Fit: 3.00x / Bony: 1.00x
  • 5.00x - Extreme
    • This preset provides extreme limits that break the mesh and can look extremely weird.
    • Limits: Heavy: 5.00x / Lean: 3.00x / Fit: 5.00x / Bony: 3.00x

Like in an unmodded game, the limits in Create-A-Sim are all a little bit less than the live-mode limits, to give the sim room to change once you begin to play.

Warnings and Known Issues

  • Only install ONE limits package at a time.
  • In Create-A-Sim, when you drag a fat or muscle slider beyond the normal limits, the sim's body will appear to stop updating. Select another item of clothing to make the body update to the new values.
  • When sims with body fat over the normal limits wear certain items of custom content clothing, their arms will clip through their body when resting at their sides. If you have any information on how custom content creators might be able to avoid this, please contact me.

Advanced settings
If you wish to choose your own customised fitness limits, read this page on advanced settings for the Expanded Fitness Limits feature.

Other mods by roBurky
The rest of my mods can be found over here.


Conflicts and Compatibility
The main mod is compatible with both the 32-bit legacy edition and 64-bit regular edition of The Sims 4.

The preset limits packages are only compatible with game versions 1.96.365 and later of the 64-bit regular edition.

The main mod overrides these script functions, and will conflict with any other mod that does the same:

  • sims.sim_info.SimInfo._get_fit_fat
  • sims.sim_info.SimInfo._set_fit_fat

The preset limits packages override this sim data resource, and will conflict with any other mod that does the same:

  • AF88EBAFBB8C2657 / Client_CASTuning_Human

Support and updates
If you like this mod, you can help it get expanded further and kept up to date with patches by becoming a patron.

To keep informed of updates to the mod, click the 'follow' button on patreon for email alerts. You can also follow roBurky on tumblr and twitter.
To talk about the mod with other players, or get live help with installing or using the mod, join our Discord server.

Become a patron

CategoryGame mod
Rated 4.7 out of 5 stars
(27 total ratings)
TagsSims 4


Download NowName your own price

Click download now to get access to the following files:

roBurky - FitnessControls.zip 64 kB
roBurky - FitnessControls-Limits-1.75x-Increased.zip 4 kB
roBurky - FitnessControls-Limits-3.00x-Exaggerated.zip 4 kB
roBurky - FitnessControls-Limits-5.00x-Extreme.zip 4 kB
roBurky - FitnessControls-Limits-1.75x-Increased.package 3 kB
roBurky - FitnessControls-Limits-3.00x-Exaggerated.package 3 kB
roBurky - FitnessControls-Limits-5.00x-Extreme.package 3 kB

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