                            PUBLISHED

UNITED STATES COURT OF APPEALS
                 FOR THE FOURTH CIRCUIT


WANDA J. STUP,                          
                  Plaintiff-Appellee,
                 v.
                                                  No. 03-2526
UNUM LIFE INSURANCE COMPANY OF
AMERICA,
             Defendant-Appellant.
                                        
          Appeal from the United States District Court
           for the District of Maryland, at Baltimore.
             William D. Quarles, Jr., District Judge.
                      (CA-02-3346-WDQ)

                      Argued: September 30, 2004

                      Decided: December 1, 2004

      Before WILKINS, Chief Judge, MOTZ, Circuit Judge,
      and Henry E. HUDSON, United States District Judge
              for the Eastern District of Virginia,
                     sitting by designation.



Affirmed by published opinion. Judge Motz wrote the opinion, in
which Chief Judge Wilkins and Judge Hudson joined.


                             COUNSEL

ARGUED: John Snowden Stanley, Jr., SEMMES, BOWEN &
SEMMES, Baltimore, Maryland, for Appellant. Michael Joseph
McAuliffe, ETHRIDGE, QUINN, MCAULIFFE, ROWAN &
HARTINGER, Rockville, Maryland, for Appellee.
2                 STUP v. UNUM LIFE INSURANCE CO.
                               OPINION

DIANA GRIBBON MOTZ, Circuit Judge:

   UNUM Life Insurance Company of America appeals from the
order of the district court granting Wanda Stup summary judgment on
her claim that UNUM improperly denied her long-term disability ben-
efits in violation of the Employee Retirement Income Security Act of
1974 (ERISA). UNUM does not dispute that Stup suffers from lupus,
fibromyalgia, and other afflictions. Rather, UNUM argues that it
acted reasonably in determining that, despite these disabilities, Stup
could perform a job commensurate with her training and, therefore,
was not entitled to long-term disability benefits under the ERISA
plan. The district court rejected this argument and concluded that
UNUM abused its discretion in denying Stup long-term benefits. For
the reasons that follow, we affirm.

                                    I.

   Lupus is a "chronic inflammatory connective tissue disorder" that
can affect the joints, skin, kidneys, lungs, heart, and blood. See The
Merck Manual 426-29 (17th ed. 1999); see also U.S. Dept. of Health
and Human Services and Nat’l Institutes of Health, Systemic Lupus
Erythematosus 3 (rev. Aug. 2003), http://www.niams.nih.gov/hi/
topics/lupus/slehandout/slehandout.pdf. Symptoms, which may come
and go, include extreme fatigue and malaise, arthritis, unexplained
fever, chest pain, pneumonia, and skin rashes. U.S. Dept. of Health
and Human Services, supra, at 3, 8-10; The Merck Manual, supra, at
426-29. Doctors use tests that detect the level of specific antibodies
in the blood and skin biopsies to diagnose lupus. U.S. Dept. of Health
and Human Services, supra, at 11-13.

   Fibromyalgia is a rheumatic disease with similar symptoms,
including "significant pain and fatigue," tenderness, stiffness of joints,
and disturbed sleep. Nat’l Institutes of Health, Questions & Answers
About Fibromyalgia 1 (rev. June 2004), http://www.niams.nih.gov/hi/
topics/fibromyalgia/Fibromyalgia.pdf. See also Ellis v. Metro. Life
Ins. Co., 126 F.3d 228, 231 n.1 (4th Cir. 1997) (quoting Taber’s
Cyclopedic Medical Dictionary (16th ed. 1989)); Sarchet v. Chater,
78 F.3d 305, 306-07 (7th Cir. 1996). Doctors diagnose fibromyalgia
                  STUP v. UNUM LIFE INSURANCE CO.                      3
based on tenderness of at least eleven of eighteen standard trigger
points on the body. Sarchet, 78 F.3d at 306. "People with rheumatoid
arthritis and other autoimmune diseases, such as lupus, are particu-
larly likely to develop fibromyalgia." Nat’l Institutes of Health, supra,
at 4. Fibromyalgia "can interfere with a person’s ability to carry on
daily activities." Id. at 1. "Some people may have such a severe case
of fibromyalgia as to be totally disabled from working, but most do
not." Sarchet, 78 F.3d at 307 (citations omitted).

   In the mid-1990s, Stup was diagnosed with lupus and fibromyalgia.1
The record reveals that a Board-certified rheumatologist, Dr. Nathan
Wei, began treating Stup in January 1996 and monitored her closely
for the next five years, examining Stup bi-weekly or monthly.

   A biopsy conducted in January 1994 verified that Stup suffered
from lupus erythematosus. Periodic lab tests consistently showed high
levels of an antibody associated with lupus in Stup’s blood. Stup’s
medical records evidence that she has suffered the following manifes-
tations of lupus: rashes, lesions, livedo, swelling, temperature fluctua-
tions, chest pains, and pneumonia.

   Stup’s fibromyalgia is also well documented. She initially
responded well to the treatment prescribed by Dr. Wei, but her condi-
tion rapidly worsened. Dr. Wei’s notes from his frequent examina-
tions of Stup state that she had diffuse trigger point tenderness and
complained of fatigue, weakness, and pain. Dr. Wei changed Stup’s
medications regularly to try to alleviate her pain, often to no avail.

   Dr. Wei recommended that Stup, along with taking prescribed
medications, "limit her activities" and "take daily naps as necessary."
But Stup disregarded his advice by continuing to work as an adminis-
trative assistant to the president of Frederick Underwriters, Inc.,
where she had been employed since 1984. In Dr. Wei’s view, Stup
"attempted to work far past her physical abilities" for several years.
By March 16, 1998, Stup’s debilitating pain and fatigue prevented her
from performing her duties. Only then did she apply for disability
benefits under Frederick’s ERISA plan.
  1
   She also suffers from Graves disease, or hyperthyroidism, degenera-
tive disc disease, and eye problems.
4                 STUP v. UNUM LIFE INSURANCE CO.
   Frederick’s plan is contained in an UNUM insurance policy, which
UNUM administers. The policy entitles a "Class 2" employee
(UNUM’s classification of Stup) to twenty-four months of disability
benefits if the insured cannot "perform each of the material duties of
h[er] regular occupation" (emphasis added). Under the policy, dis-
ability benefits for Class 2 employees cease after two years unless
"the insured cannot perform each of the material duties of any gainful
occupation for which [s]he is reasonably fitted by training, education
or experience" (emphasis added). UNUM paid Stup disability benefits
from September 1998 until November 2000, at which time it termi-
nated her benefits, explaining that "[s]ince the definition of disability
now applies to ‘any occupation’ we feel you could return to work in
a sedentary occupation."

   Stup appealed UNUM’s denial of long-term disability benefits. In
support of her appeal, she submitted her voluminous medical records
and an UNUM Estimated Functional Abilities Form filled out by Dr.
Wei, stating she could lift only one to ten pounds occasionally and
was "unable to perform even sedentary [sic] for more than 1-2 hours
at a time."

   UNUM referred her medical file to Dr. Parke, an in-house physi-
cian, who determined that "[b]ased on medical (objective) studies,
Ms. Stup has evidence of a [Connective Tissue Disorder]." He con-
cluded that the "best way to fully assess" her ability to work "would
be a visual assessment, possibly coordinated" with a physical and
rheumatological independent medical examination. Instead of follow-
ing this recommendation, UNUM’s associate medical director, Dr.
Bielawski, decided to obtain a Functional Capacity Evaluation (FCE).
Accordingly, UNUM requested that Dr. Wei write Stup a prescription
for an FCE, which he did.

   On April 3, 2001, a physical therapist conducted the FCE. The
therapist reported that Stup’s flexibility and range of motion were
within functional limits but that she "[e]xhibited pain behaviors dur-
ing testing." The therapist could not measure Stup’s strength because
Stup "g[a]ve out" before an adequate assessment could be made. Sim-
ilarly, the therapist could not determine Stup’s aerobic capacity
because Stup could not move "at the minimum speed necessary for
the treadmill walking test (2.0 mph)." Stup was able to walk "for 4.5
                  STUP v. UNUM LIFE INSURANCE CO.                       5
minutes at a speed of 1.2 mph prior to stopping the test due to hip and
leg pain"; she averaged about 7.5 pounds of grip strength with her
right hand, and 11.1 pounds with her left. Tests also showed that she
could occasionally lift 16.5 pounds from floor to knuckle, 12.5
pounds from knuckle to shoulder, and 7.5 pounds from shoulder to
overhead and could carry 12.5 pounds for 100 feet. Stup performed
inconsistently on squat lift, isometric pull, and hand grip tests, which
the therapist interpreted as a sign that Stup did not make a consistent
effort. The FCE did not measure Stup’s positional tolerance because
after the remaining tests were explained to her, Stup "indicated she
did not feel she could go on" and the physical therapist "agreed that
testing should not continue."

   In total, the Functional Capacity Evaluation lasted only two and a
half hours. The physical therapist opined that "[t]he results of this
evaluation indicate" that Stup could perform sedentary work, but
immediately cautioned that "the results of this evaluation may not be
truly indicative of the clients [sic] functional capabilities." The thera-
pist noted "inconsistencies" that "became apparent in the examina-
tion." For example, Stup showed stronger grip strength in her left
hand than her right even though she is right handed and the dominant
hand is usually ten to fifteen percent stronger than the other. The ther-
apist also pointed out that at the time Stup complained of severe pain,
her heart rate was lower than it had been after thirty minutes of sit-
ting. The physical therapist concluded "it would not be prudent to
make recommendations regarding specific job duties that this client
can or cannot perform due to a lack of consistent and true informa-
tion."

   Nevertheless, an UNUM doctor, Burton McDaniel, after stating
that he reviewed Stup’s file "with special attention to recent FCE,"
concluded that the FCE "appears to be very thorough and valid" and
the results "concur with the statement that she is capable of perform-
ing sedentary level work." His one-paragraph report focused entirely
on the FCE test results. Using as a baseline the measurement of
Stup’s heart rate during a stress test taken the previous year, which
was referred to in the FCE, the doctor implied Stup had not given a
full effort during the FCE because if she had, her heart rate would
have been higher during testing. He concluded that "[w]ithout incon-
sistencies claimant may well be able to function at a higher work level
6                 STUP v. UNUM LIFE INSURANCE CO.
such as light." UNUM then informed Stup that its initial decision "to
deny [her] claim was appropriate."

   Stup asked UNUM to review its decision a second time, challeng-
ing UNUM’s assertion that she could perform sedentary work.2 In
support of her appeal, Stup submitted an affidavit in which she
explained her daily activities:

    On an average day, I don’t go anywhere. I go outside in the
    morning to get to the mailbox, have breakfast and then read
    or nap, depending on my pain level. I try to stay awake in
    the morning and sometimes I will make efforts to pick up
    around the house. My daughter helps me clean up, and I try
    to do a little bit each day. Some days I cannot do any clean-
    ing or picking up because of the pain; other days I can do
    a few minutes. I cannot do any type of "normal" house
    chores at a "normal" pace. I only live in one half of my
    house because there is no way that I could take care of a
    house. Sometimes I eat a light lunch and sometimes I skip
    lunch. Then I take my pain medication and lay down for the
    afternoon. I watch the news, and on some days I go sit out-
    side on the front porch and read. I eat dinner sometimes. I
    then watch TV or sit on the porch.

Stup also stated in her affidavit that she had offered to try to continue
the tests for the FCE, but the physical therapist "said that she’d rather
   2
     Stup also challenged her classification as a Class 2 employee. The
UNUM policy defines a "Class 1" employee as an officer or manager
earning over $35,000 per year and a "Class 2" employee as everyone
else. The policy entitles a Class 1 employee to disability benefits for
unlimited duration as long as she "cannot perform all of the material
duties of h[er] regular occupation"; in contrast, a Class 2 employee is
entitled to benefits for more than two years only if she cannot "perform
each of the material duties of any gainful occupation for which [s]he is
reasonably fitted by training, education or experience." Stup argued that
her claim should have been evaluated as though she were a Class 1 par-
ticipant because she was an assistant secretary of the board of directors
and made more than $35,000 a year when the $100 in salary she declined
each month in order to use a company car was taken into account. The
district court did not need to resolve this question, nor do we.
                 STUP v. UNUM LIFE INSURANCE CO.                       7
I not start the tests if I wasn’t going to complete them, and that she
didn’t think I was going to make it."

  In addition, Stup provided UNUM with a detailed letter from Dr.
Wei dated August 20, 2001, explaining his diagnosis and opinion that
Stup could not perform even sedentary work:

    Ms. Stup’s fibromyalgia diagnosis is supported by the fol-
    lowing criteria: positive reaction to all trigger points, nine
    positive tender points, non-restorative sleep, short term
    memory deficiency, aches and pains with minimal activity,
    and severe, persistent fatigue on minimal exertion. Ms.
    Stup’s fatigue is best described as profound and prevents her
    from being able to perform normal daily activities, such as
    personal grooming and household chores, without experi-
    encing draining, marked loss of energy. Her short-term
    memory deficiency is evident in her inability to remember
    simple directions and the purpose for which she sets out on
    driving excursions.

       In addition to fibromyalgia, Ms. Stup suffers from low
    back pain that radiates down her legs as a result of degener-
    ative disc disease. As for her lupus erythematosus, the most
    significant symptom is limited mobility and pain in both her
    hands.

       I have recommended to Ms. Stup that she limit her activi-
    ties, take daily naps as necessary to replenish her energy
    level, and continue with medications and follow-up treat-
    ment to document and monitor her symptoms. Despite my
    recommendations, she attempted to work far past her physi-
    cal abilities. I have explained to her that she will experience
    symptom flare-ups and periodic improvement relative to her
    baseline condition. I also explained that the ability to predict
    when she may experience flare-ups or periods of improve-
    ment is minimal at best.

      Based upon my history of treatment with Ms. Stup, I do
    not believe that she is physically capable of performing even
    sedentary work. She must be able to perform physical activi-
8                 STUP v. UNUM LIFE INSURANCE CO.
    ties at her own pace with frequent rest periods; she needs to
    nap on a daily basis; and she will suffer an exacerbation of
    symptoms as a result of stress common in any workplace.
    Furthermore, as a result of fatigue and back pain, she is lim-
    ited in her ability to stand, sit or walk for periods of time
    greater than thirty (30) minutes. I recommend against repeti-
    tive bending, kneeling, crawling, and climbing stairs. She is
    also limited in her ability to lift, carry, push or pull more
    than ten (10) pounds. The limitation of the use of her hands
    makes anything more than simple grasping beyond her abil-
    ity. . . .

       Ms. Stup has never shown herself to be a malingerer or
    less than fully motivated to do whatever is necessary to
    improve her health. She is compliant with all recommenda-
    tions for treatment, except to the extent that she worked past
    the time that it was advisable for her to do so. It is my pro-
    fessional opinion that Ms. Stup is totally disabled from all
    work. This total disability from all work has been present
    since March 16, 1998. Due to the chronic nature of her con-
    dition, [sic] will be totally disabled to work into the foresee-
    able future.

   An in-house UNUM doctor, Maureen Lee, reviewed Dr. Wei’s let-
ter to determine whether it should affect UNUM’s "prior opinion that
claimant has sedentary work capacity." On a brief form, the doctor
stated that because it was not accompanied by new objective testing,
"[t]he updated medical letter does not change the prior conclusions to
the file (based on FCE 4-4-01)." UNUM again denied Stup’s disabil-
ity claim.

   Having exhausted her administrative appeals, Stup filed this suit,
claiming UNUM violated ERISA by wrongfully denying her long-
term disability benefits. After consideration of memoranda submitted
by the parties, the district court granted summary judgment to Stup.
UNUM appeals.

                                  II.

   We review the grant of summary judgment de novo, "employing
the same standards applied by the district court" in reviewing the fidu-
                  STUP v. UNUM LIFE INSURANCE CO.                       9
ciary’s decision to deny ERISA benefits. See Sheppard & Enoch
Pratt Hosp., Inc. v. Travelers Ins. Co., 32 F.3d 120, 123 (4th Cir.
1994) (citation omitted). Two facts affect which standard we apply in
reviewing UNUM’s decision to deny ERISA benefits.

   First, the ERISA plan (Frederick Underwriters’ insurance policy
with UNUM) provided UNUM with "the discretionary authority both
to determine an employee’s eligibility for benefits and to construe the
terms of this policy." Although this grant of authority is not as broad
as that in some ERISA plans, see, e.g., Booth v. Wal-Mart Stores,
Inc., 201 F.3d 335, 343 (4th Cir. 2000), it does invest UNUM with
discretion. When an ERISA plan affords an administrator discretion,
a court reviews the administrator’s decision to deny benefits for an
abuse of that discretion, asking whether the denial of benefits was rea-
sonable, Bernstein v. CapitalCare, Inc., 70 F.3d 783, 787 (4th Cir.
1995) (citation omitted), "based on the facts known to [the adminis-
trator] at the time."3 Sheppard & Enoch Pratt Hosp., 32 F.3d at 125.
An administrator’s decision is reasonable "if it is the result of a delib-
erate, principled reasoning process and if it is supported by substantial
evidence." Bernstein, 70 F.3d at 788 (internal quotation marks and
citation omitted).

   The other fact determinative of the appropriate standard of judicial
review is that in denying benefits, UNUM acted under a conflict of
interest. That is, its decision to deny benefits impacted its own finan-
cial interests because it "both administers the plan and pays for bene-
fits received by its members." Id. at 788; see also Doe v. Group
Hospitalization & Med. Servs., 3 F.3d 80, 86 (4th Cir. 1993). As we
noted in Booth, the Supreme Court has directed that this conflict
"must be weighed in determining whether there is an abuse of discre-
tion." Booth, 201 F.3d at 342 (emphasis in original) (citing Firestone
  3
   Therefore, in reviewing UNUM’s decision, a court cannot consider
evidence that was not before UNUM when it made its determination.
Accordingly, although Stup urges us to consider Dr. McDaniel’s deposi-
tion in which he conceded that he did not recall reviewing any informa-
tion in Stup’s file other than the FCE test, and acknowledged that "an
inconsistency of effort finding" in an FCE "can be indicative of a flare
up having occurred in a particular part of the body," neither we nor the
district court have considered this evidence.
10                STUP v. UNUM LIFE INSURANCE CO.
Tire & Rubber Co. v. Bruch, 489 U.S. 101, 115 (1989)). In these cir-
cumstances, "we will not act as deferentially as would otherwise be
appropriate. . . . [T]he fiduciary decision will be entitled to some def-
erence, but this deference will be lessened to the degree necessary to
neutralize any untoward influence resulting from the conflict." Doe,
3 F.3d at 87; accord Ellis v. Metro. Life Ins. Co., 126 F.3d 228, 233
(4th Cir. 1997); Bedrick v. Travelers Ins. Co., 93 F.3d 149, 152 (4th
Cir. 1996) (citing Bailey v. Blue Cross & Blue Shield, 67 F.3d 53, 56
(4th Cir. 1995)). Under this sliding-scale standard of review, "[t]he
more incentive for the administrator or fiduciary to benefit itself by
a certain interpretation of benefit eligibility or other plan terms, the
more objectively reasonable the administrator or fiduciary’s decision
must be and the more substantial the evidence must be to support it."4
Ellis, 126 F.3d at 233.

                                   III.

  We cannot hold that UNUM’s decision to deny benefits was either
supported by substantial evidence or the product of a principled rea-
soning process.

   Stup has offered overwhelming and uncontradicted evidence that
she suffers from lupus and fibromyalgia, as well as a number of other
afflictions. UNUM does not dispute or question this evidence. Rather
UNUM insists Stup’s ailments do not render her unable to perform
sedentary work commensurate with her training.

  On this issue, Stup submitted her medical records and the detailed
opinion of Dr. Nathan Wei, the Board-certified rheumatologist who
had treated her for years. Dr. Wei reported that Stup’s fibromyalgia
  4
   Stup has submitted evidence that she maintains shows the "‘medical
review’ process conducted by UNUM was so biased and one-sided as to
be deserving of no deference whatsoever." She points to the deposition
given in another case by a former UNUM medical director, Dr. Patrick
McSharry, who stated it was UNUM’s "‘primary practice and policy to
deny disability claims’" and that UNUM "‘medical advisors were used
only to provide language and conclusions supporting the denial of the
claims.’" The district court does not appear to have found it necessary or
appropriate to rely on this evidence, nor do we.
                  STUP v. UNUM LIFE INSURANCE CO.                    11
caused her "non-restorative sleep, short-term memory deficiency,
aches and pains with minimal activity, and severe, persistent fatigue,"
concluding that her fatigue and memory loss prevent her from "being
able to perform normal daily activities" or "remember simple direc-
tions." Dr. Wei also concluded that Stup’s degenerative disc disease
caused "low back pain that radiates down her legs" and that her lupus
erythematosus caused "limited mobility and pain in both her hands."
He said she cannot use her hands for more than simple grasping and
her ability to lift, carry, push, or pull is severely limited.

   Dr. Wei explained that he had urged Stup to limit her activities and
"take daily naps as necessary to replenish her energy level," but that
she had "attempted to work far past her physical abilities." He stated
Stup "must be able to perform physical activities at her own pace with
frequent rest periods," and "stress common in any work place" would
"exacerbat[e]" her symptoms. Dr. Wei concluded that Stup is not
"physically capable of performing even sedentary work"; rather in his
"professional opinion" she is "totally disabled from all work." Stup’s
medical records substantiated her long history of and treatment for
these disabilities.

   Unquestionably, this evidence satisfies Stup’s initial burden of sub-
mitting proof that she could not perform even sedentary work and was
entitled to long-term benefits under the ERISA plan. Just as clearly,
this evidence would not require UNUM to award benefits if it had
"substantial evidence" that Stup could perform sedentary work. Bern-
stein, 70 F.3d at 788 (internal quotation marks and citation omitted).
And as UNUM correctly notes, an administrator does not act unrea-
sonably by denying benefits if the record contains "conflicting medi-
cal reports." Elliott v. Sara Lee Corp., 190 F.3d 601, 606 (4th Cir.
1999).

   UNUM maintains that it acted reasonably in denying benefits
because the record contains conflicting medical evidence as to Stup’s
ability to work. But UNUM ignores that while an administrator does
not necessarily abuse its discretion by resolving an evidentiary con-
flict to its advantage, the conflicting evidence on which the adminis-
trator relies in denying coverage must be "substantial" — especially
when, as in this case, the administrator has an economic incentive to
12                 STUP v. UNUM LIFE INSURANCE CO.
               5
deny benefits. See Ellis, 126 F.3d at 233-34 (finding administrator
with incentive to deny benefits acted reasonably in doing so because
even though several doctors said insured was disabled, it had "sub-
stantial evidence" that her doctors did not agree on the proper diagno-
sis and three independent medical panels "concluded that there was
no conclusive diagnosis"). For example, an administrator operating
under a conflict of interest does not act reasonably in denying benefits
if faced, on the one hand, with substantial evidence of disability and,
on the other, with only tentative and ambiguous evidence that might,
or might not, favor denial of benefits. This is precisely the situation
at hand.

   UNUM claims the FCE conflicts with Dr. Wei’s assessment, insist-
ing the FCE "unequivocally" shows that Stup can perform sedentary
work. But there is nothing unequivocal about the results of Stup’s
FCE — indeed, the physical therapist explicitly equivocated, noting
the inconsistency of the test results, in the course of ultimately offer-
ing her negative interpretation. Upon examination, it is clear that the
FCE test results either supported Dr. Wei’s assessment or were, at the
very least, ambiguous; the results certainly do not provide substantial
evidence that Stup could perform sedentary work.

   First, and most obviously, the FCE lasted only two and a half
hours, so the FCE test results do not necessarily indicate Stup’s ability
to perform sedentary work for an eight- (or even four-) hour workday,
five days a week. Even if the results of the FCE had shown conclu-
  5
    UNUM confuses this substantiality requirement with the "treating
physician" rule outlawed in Black & Decker Disability Plan v. Nord, 123
S. Ct. 1965 (2003). UNUM argues that the district court "erroneously
applied" the treating physician rule. The argument is meritless. The dis-
trict court did not "require" UNUM "to accord special weight to the opin-
ions of [the] claimant’s physician," which Nord prohibits. Id. at 1972.
Rather, the district court simply concluded that UNUM failed to adhere
to the substantiality requirement by arbitrarily disregarding Stup’s reli-
able evidence, including the opinion of her treating physician, relying
instead on ambiguous and insubstantial evidence favoring UNUM’s own
economic self-interest. It is thus UNUM, not Stup, that has failed to fol-
low an instruction of the Nord Court, i.e., that "[p]lan administrators
. . . may not arbitrarily refuse to credit a claimant’s reliable evidence,
including the opinions of a treating physician." Id.
                  STUP v. UNUM LIFE INSURANCE CO.                     13
sively that Stup could perform sedentary tasks for the duration of the
test, which they do not, those results provide no evidence as to her
abilities for a longer period. Perhaps that is why Dr. Parke — the first
UNUM in-house doctor to review Stup’s file and who agreed with Dr.
Wei’s diagnosis — thought that observing Stup as she performed her
daily routine would provide the "best" method for determining her
ability to work.

   Second, Stup’s performance on the FCE may actually substantiate
rather than conflict with Stup’s evidence as to her inability to work.
Based on his diagnosis, the accuracy of which is not in dispute, Dr.
Wei concluded that, due to pain and fatigue, Stup could not perform
sedentary work for more than one or two hours at a time, had limited
ability to lift or carry more than ten pounds, and could not sit or walk
for more than thirty minutes at a time. Consistent with Dr. Wei’s
assessment, during the FCE Stup exhibited pain when her flexibility
and range of motion were tested. She "gave out" before her strength
could be measured. She could not walk fast enough for the physical
therapist to assess her aerobic capacity, and she could only walk for
four and a half minutes at 1.2 miles per hour before succumbing to
hip and leg pain. The physical therapist halted the testing after only
two and a half hours because it did not appear that Stup could com-
plete the tests, suggesting Stup’s exertion could not be sustained for
much longer than two and a half hours. These results entirely
accorded with Stup’s evidence. Thus the actual results of the FCE
cannot be said to conflict with Dr. Wei’s conclusions and they surely
do not provide substantial evidence conflicting with Dr. Wei’s assess-
ment.

   In fact, the only "evidence" UNUM offered that Stup could per-
form sedentary work is the physical therapist’s equivocal and tenta-
tive interpretation of the FCE results and Dr. McDaniel’s concurrence
in that interpretation.6 But this "evidence" is neither "substantial" nor
  6
   UNUM misleadingly contends that in concluding Stup could perform
sedentary work, it "relied upon medical information in the form of opin-
ions" of "four other physicians." Actually, three of these four UNUM in-
house physicians, Drs. Parke, Bielawski, and Lee, expressed absolutely
no view as to whether Stup could perform sedentary work. Dr. Parke rec-
14                STUP v. UNUM LIFE INSURANCE CO.
the product of the type of "deliberate, principled reasoning process"
indicative of a reasonable determination. Bernstein, 70 F.3d at 788
(internal quotation marks and citation omitted).

   An equivocal opinion — especially one based on ambiguous test
results — simply does not provide "substantial evidence." Here, the
physical therapist herself twice expressly recognized the ambiguity of
the FCE results and hedged her negative interpretation of them. Ini-
tially, she warned that Stup’s inconsistent test results "may not be
truly indicative of the clients [sic] functional capabilities." And in
conclusion, the therapist cautioned, "it would not be prudent to make
recommendations regarding specific job duties that this client can or
cannot perform due to a lack of consistent and true information."

   Moreover, we cannot say that the reasoning of UNUM’s in-house
doctor, Dr. McDaniel, was "deliberate" or "principled" here.7 After
reviewing the FCE, but without ever seeing or examining Stup or

ognized that Stup evidenced a connective tissue disorder, but did not
assess her ability to perform sedentary work; instead, he recommended
a visual assessment and physical examination as "the best way to fully
assess" this. Dr. Bielawski, without himself assessing Stup’s ability to
work, rejected this recommendation and decided to ask for an FCE to
assess her ability to work. Similarly, Dr. Lee made no assessment as to
Stup’s ability to work; rather, she simply stated that Dr. Wei’s updated
letter should not affect UNUM’s "prior conclusions" as to Stup’s ability
to work.
   7
     We note that the tacit conclusion of the physical therapist and Dr.
McDaniel that the inconsistent test results demonstrated malingering by
Stup ignores undisputed evidence in the medical files submitted by Stup.
Examination of these files indicates that the examples the therapist and
Dr. McDaniel pointed to as evidence of Stup’s purposefully inconsistent
effort could well have resulted from her true inability to perform due to
debilitating pain and fatigue. For instance, the therapist and Dr. McDan-
iel found it suspicious that Stup displayed greater strength in her left
hand than in her right, since she is right-handed. But that result hardly
seems suspicious in view of the fact that an MRI of Stup’s right hand
revealed that "[t]here is evidence of an erosive arthropathy and synovitis
involving the proximal interphalangeal joints," which could explain why
she displayed greater strength in her left hand than her right.
                   STUP v. UNUM LIFE INSURANCE CO.                        15
even acknowledging the physical therapist’s warning that it would not
be "prudent" to use the FCE results to determine Stup’s ability to per-
form "specific job duties," Dr. McDaniel simply stated that the test
results "concur[red] with the statement that she is capable of perform-
ing sedentary work" — ignoring that the test results could be inter-
preted just as easily as consistent with Dr. Wei’s conclusion that Stup
could not work. Thus, UNUM’s doctor created conflicting "evidence"
by disregarding the testgiver’s own admonition as to the possible
unreliability of the FCE and interpreting the results against the claim-
ant when they could be read as entirely consistent with the medical
evidence demonstrating disability.8

   In sum, the only "evidence" that UNUM offered to justify its denial
of long term benefits to Stup simply does not constitute "substantial
evidence" arrived at after a "deliberate, principled reasoning process"
— especially given that UNUM acted under a conflict of interest. See
Bernstein, 70 F.3d at 788 (internal quotation marks and citation omit-
ted). Thus, the district court did not err in finding UNUM abused its
discretion in denying Stup long-term disability benefits.

                                    IV.

   Stup provided UNUM with years of substantial medical evidence
supporting her diagnosis, which UNUM does not dispute, and her
doctor’s well-documented conclusion that she could not work.
UNUM argues it acted reasonably in denying Stup benefits because
it relied on evidence conflicting with her long-time physician’s sub-
stantiated opinion that her medical condition significantly limited her
capabilities. But the so-called conflicting evidence, upon examination,
  8
    Contrary to UNUM’s suggestion, this "evidence" differs dramatically
from that relied on in Booth and Elliott, on which UNUM so heavily
relies. See Elliott, 190 F.3d at 606 (noting that the statement of the claim-
ant’s primary physician that she could not return to work was contra-
dicted by four doctors who had treated her, including the primary
physician, whose own prior statements suggested the claimant could per-
form sedentary work); Booth, 201 F.3d at 338-39, 344-45 (noting that
claimant’s treating physician’s own notes and the heart medication he
had prescribed previously for the insured contradicted his insistence dur-
ing litigation that she did not have a preexisting heart condition).
16                 STUP v. UNUM LIFE INSURANCE CO.
fully supports the opinion of Stup’s Board-certified rheumatologist or
is, at the very least, so ambiguous that the person administering the
FCE thought the test results were not a prudent basis for assessing
Stup’s specific job capabilities. Thus the evidence on which UNUM
relies is neither substantial nor conflicting.

     Accordingly, the judgment of the district court is

                                                          AFFIRMED.
