T Nation

Temperature and refeed

I’ve heard you should take your temperature in the morning when dieting. If it goes down, then you should have a “re-feed” day. Is that an accurate way to measure fat burning or thyroid activity?


No, it’s not. Check out one of Cy’s latest columns; he touches on this. I believe he stated that it would be akin to measuring sexual function by whether or not you have a morning erection.

Take care,


Hi Paul,
Body temperature is a very crude way to assess basal metabolic rate changes. Although you may have heard of its use regarding athletes who use thermogenic drugs/ supplements (e.g. where it plays a more obvious role regarding [beta] adrenalin receptor down-regulation), it is - at best - only an adjunct measure for most dieters. The hypothalamus controls body temp pretty tightly. Oral temps may offer a little supportive info., however, when used along with other measures like body weight changes and body composition (e.g. skinfold) results. Many things affect body temp.: recent meals particularly within 4 hours, ambient temperature, various suupplements, various foods (some more than others), non-thyroid hormonal fluctuations, injury, infections, stress, etc.

The main reason you may have seen this crude measure suggested on T-mag is because the vast majority of folks cannot easily get thyroid (T3) testing done on a whim. That would, however, be the obvious valid choice for a dieter aside from a metabolic cart - but of course these measures are largely inaccessible.


Depends on who you ask. There are medical treatments and professionals that do rely on using body temperature to assess thyroid function, which is a reliable indicator of metabolic rate. There are other medical professionals who disagree and use strictly blood tests instead. If you ask those who actually suffer from thyroid related conditions and have used both forms of treatment most of them seem to like the body temperature method. Although blood tests should be more accurate perhaps many MD’s do a poor job interpreting them. Bottom line is the body temperature can be influenced by many things, but if you monitor it closely before during and after your diet if it’s going down your metabolic rate will likely be going down as well. The actual optimum temperature will vary depending on whether you do an oral or basal body temp and you have to use a good thermometer and measure only first thing in the morning. Also you’ll need to establish a baseline temperature prior to starting your diet. Generally, most people will run a morning oral temp between 97-98 and function and feel best at that temp although some will feel perfectly normal at 96, that’s the importance of the baseline. I would say a drop of .5 or more would be indicative of possible depressed thyroid and metabolic rate and in such the case a re-feed may be optimal.