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Do fat people stay warmer than thin people?
Pack on some extra pounds for winter
By Daniel Engber
01.02.2014
At the yearly Rottnest Channel Swim in Western Australia,
participants often smear their bodies with animal fat for
insulation against the 70-degree water. But their own body fat
also helps to keep them warm, like an extra layer of clothing
beneath the skin. When scientists studied aspects of the event in
2006, they found that swimmers with a greater body mass index
(BMI) appear to be at much lower risk of getting hypothermia.
The same effect has been demonstrated in hospitals
where patients who’ve suffered cardiac arrest are treated
with “therapeutic hypothermia” to stave off brain injury and
inflammation. Studies have shown that it takes longer to induce
hypothermia in obese patients than in their leaner counterparts.
The extra fat seems to insulate the body’s core.
Under certain conditions, though, overweight people might
feel colder than people of average weight. That’s because the
brain combines two signals — the temperature inside the body
and the temperature on the surface of the skin — to determine
when it’s time to constrict blood vessels (which limits heat loss
through the skin) and trigger shivering (which generates heat).
And since subcutaneous fat traps heat, an obese person’s core
will tend to remain warm while his or her skin cools down.
According to Catherine O’Brien, a research physiologist with
the U.S. Army Research Institute of Environmental Medicine, it’s
possible that the lower skin temperature would give fatter people
the sense of being colder overall.
But O’Brien points out that many other factors beyond
subcutaneous fat help determine the rate at which we chill.
Smaller people, who have more surface area compared to the
total volume of their bodies, lose heat more quickly. (It’s often
said that women feel colder than men; average body size may
play a part.) A more muscular physique may also offer some
protection against hypothermia, partly because muscle tissue
generates lots of heat. “We have a joke around here that the
person who’s best-suited for cold is fit and fat,” says O’Brien.
(www.popsci.com)
Leia o texto para responder à questão.
Do fat people stay warmer than thin people?
Pack on some extra pounds for winter
By Daniel Engber
01.02.2014
At the yearly Rottnest Channel Swim in Western Australia, participants often smear their bodies with animal fat for insulation against the 70-degree water. But their own body fat also helps to keep them warm, like an extra layer of clothing beneath the skin. When scientists studied aspects of the event in 2006, they found that swimmers with a greater body mass index (BMI) appear to be at much lower risk of getting hypothermia.
The same effect has been demonstrated in hospitals where patients who’ve suffered cardiac arrest are treated with “therapeutic hypothermia” to stave off brain injury and inflammation. Studies have shown that it takes longer to induce hypothermia in obese patients than in their leaner counterparts. The extra fat seems to insulate the body’s core.
Under certain conditions, though, overweight people might feel colder than people of average weight. That’s because the brain combines two signals — the temperature inside the body and the temperature on the surface of the skin — to determine when it’s time to constrict blood vessels (which limits heat loss through the skin) and trigger shivering (which generates heat). And since subcutaneous fat traps heat, an obese person’s core will tend to remain warm while his or her skin cools down. According to Catherine O’Brien, a research physiologist with the U.S. Army Research Institute of Environmental Medicine, it’s possible that the lower skin temperature would give fatter people the sense of being colder overall.
But O’Brien points out that many other factors beyond subcutaneous fat help determine the rate at which we chill. Smaller people, who have more surface area compared to the total volume of their bodies, lose heat more quickly. (It’s often said that women feel colder than men; average body size may play a part.) A more muscular physique may also offer some protection against hypothermia, partly because muscle tissue generates lots of heat. “We have a joke around here that the person who’s best-suited for cold is fit and fat,” says O’Brien.
(www.popsci.com)
Gabarito comentado
Resposta correta: E
Tema central: o texto trata da relação entre gordura corporal e temperatura — ou seja, se pessoas com mais gordura ficam mais aquecidas — usando evidências científicas e explicações fisiológicas. Para resolver a questão é preciso identificar como o título e o subtítulo orientam a resposta ao leitor, diferenciando pergunta retórica de indicação de resposta.
Resumo teórico e conceitos-chave: gordura subcutânea atua como isolamento térmico e retarda perda de calor; o cérebro integra temperatura interna e da pele para regular vasoconstrição e tremores; razão superfície/volume influencia perda de calor (pessoas menores esfriam mais). Fontes citadas no texto: PopSci e U.S. Army Research Institute of Environmental Medicine; conceito de termorregulação está em manuais de fisiologia (ex.: Guyton & Hall).
Justificativa da alternativa correta (E): O subtítulo do texto é "Pack on some extra pounds for winter" — frase que, em inglês, recomenda engordar para o inverno. Isso sugere uma resposta positiva à pergunta do título ("Do fat people stay warmer than thin people?"), ou seja, aponta que ganhar peso/ter mais gordura ajuda a ficar mais aquecido. Logo, o subtítulo dá uma indicação favorável à ideia levantada no título, o que torna a alternativa E correta.
Análise das alternativas incorretas:
A — Afirma que a obesidade é alvo de crítica como forma não saudável de se manter aquecido. Errado: o texto não critica o emagrecimento/obesidade; discute efeitos térmicos da gordura e pondera fatores adicionais. Não há julgamento moral ou recomendação de que a obesidade seja uma prática condenável.
B — Diz que o subtítulo sugere que as pessoas emagreçam para enfrentar o inverno. Errado: o subtítulo sugere o oposto — “Pack on some extra pounds” significa ganhar peso, não emagrecer.
C — Alega que a pergunta do título induz uma opinião negativa sobre obesidade. Errado: a pergunta é neutra/investigativa; não contém avaliação negativa. O texto explora prós e contras do efeito térmico da gordura.
D — Afirma que as pesquisas aplicam-se apenas ao inverno na Austrália. Errado: o exemplo da natação em Austrália é um caso, mas o texto cita estudos clínicos e princípios gerais (hospital, termorregulação), mostrando que os achados têm aplicação mais ampla, não restrita ao inverno australiano.
Dicas de interpretação para provas: foque em relação entre título e subtítulo; traduza frases curtas do subtítulo (atenção a verbos imperativos/conselhando); busque no texto frases que confirmem se a sugestão do subtítulo é apoiada. Evite inferir juízos que o autor não expressa.
Fontes mencionadas no próprio texto: PopSci; U.S. Army Research Institute of Environmental Medicine. Para aprofundar, consulte manuais de fisiologia (ex.: Guyton & Hall) sobre termorregulação.
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