Stofskiftet ødelægges?

[Stubbe]

På det sidste er det næsten dagligt at der skrives herinde, at stofskiftet går i stå, stofskiftet ødelægges, osv.

Er der nogen som kan forklare hvad der sker, henvise til noget litteratur hvor det er beskrevet, referere til studier som viser eller tyder på det?

[Cyriz]

Er også meget interesseret i dette spørgsmål...

Jeg oprettede en tråd om emnet for nogle måneder tilbage, hvor der ligesom blev taget "hul på bylden"

Tråden kan findes HER

Vil dog mene at du selv har fat på noget af det rigtige med din tidligere udtalelse, Stubbe

Stofskiftet "ødelægges" ikke ved diæt. Det er klart man påvirkes, en form for adaptation, men dette er kun så længe diæten varer og er afhængig af især restriktionen og varigheden.

[Ugh Togoth]

Ja det er et meget centralt og interessant spørgsmål i forhold til vægttab, om der forekommer en form for nedregulering, og i så fald i hvilke tilfælde, og hvor markant denne er.

Jeg husker godt den anden tråd, hvor der desværre ikke kom nogen afklaring.

De eneste to undersøgelser jeg umidelbart ligger inde med er omkring nedregulering og leptinniveau.

Low-dose leptin reverses skeletal muscle, autonomic, and neuroendocrine adaptations to maintenance of reduced weight.

Rosenbaum M, Goldsmith R, Bloomfield D, Magnano A, Weimer L, Heymsfield S, Gallagher D, Mayer L, Murphy E, Leibel RL.

Columbia University College of Physicians and Surgeons, New York, New York 10032, USA. [email protected]

Maintenance of a reduced body weight is accompanied by decreased energy expenditure that is due largely to increased skeletal muscle work efficiency. In addition, decreased sympathetic nervous system tone and circulating concentrations of leptin, thyroxine, and triiodothyronine act coordinately to favor weight regain. These "weight-reduced" phenotypes are similar to those of leptin-deficient humans and rodents. We examined metabolic, autonomic, and neuroendocrine phenotypes in 10 inpatient subjects (5 males, 5 females [3 never-obese, 7 obese]) under 3 sets of experimental conditions: (a) maintaining usual weight by ingesting a liquid formula diet; (B) maintaining a 10% reduced weight by ingesting a liquid formula diet; and © receiving twice-daily subcutaneous doses of leptin sufficient to restore 8 am circulating leptin concentrations to pre-weight-loss levels and remaining on the same liquid formula diet required to maintain a 10% reduced weight. During leptin administration, energy expenditure, skeletal muscle work efficiency, sympathetic nervous system tone, and circulating concentrations of thyroxine and triiodothyronine returned to pre-weight-loss levels. These responses suggest that the weight-reduced state may be regarded as a condition of relative leptin insufficiency. Prevention of weight regain might be achievable by strategies relevant to reversing this leptin-insufficient state.

http://www.ncbi.nlm.nih.gov/entrez/query.f...l=pubmed_docsum

Low dose leptin administration reverses effects of sustained weight-reduction on energy expenditure and circulating concentrations of thyroid hormones.

Rosenbaum M, Murphy EM, Heymsfield SB, Matthews DE, Leibel RL.

Columbia University, New York, New York, USA.

Maintenance of a reduced body weight is associated with decreased 24-hour energy expenditure, and decreased circulating concentrations of leptin and thyroid hormones. To determine whether these adaptive metabolic and endocrine changes are partly leptin-mediated, we measured body composition, aspects of energy expenditure, and circulating concentrations of leptin and thyroid hormones in 4 subjects at 3 time points: 1.) Usual body weight; 2.) While stable at 10% reduced body weight; and 3.) During a 5-week period at 10% reduced body weight while receiving twice per day leptin injections that restored 8 AM circulating leptin concentrations to those seen at usual body weight. During maintenance of a 10% reduced body weight, circulating T3, T4, and leptin concentrations were decreased. All of these endocrine changes were reversed by administration of "replacement" doses of leptin (r-metHuLeptin). Indirect calorimetry, and subtle changes in body composition associated with leptin administration, were used to calculate the net change in stored calories and in 24-hour energy expenditure. Total energy expenditure increased in all subjects during r-metHuLeptin administration. These data indicate that decrease leptin concentrations resulting from loss of fat mass account for some aspects of the endocrine/metabolic phenotype associated with the weight-reduced state.

http://www.ncbi.nlm.nih.gov/entrez/query.f...3&dopt=Abstract